Health ConditionsThe American Dental Association defines halitosis as a combination of the Latin and Greek words halitus (breath) and osis (pathological process), referring to a condition that causes an unpleasant odor in exhaled air. More broadly, halitosis is defined as the presence of an unpleasant odor in exhaled air, regardless of its cause.
Halitosis is categorized into genuine halitosis, pseudo-halitosis, and halitophobia. Genuine halitosis is a socially unacceptable form of malodor, while pseudo-halitosis is a condition in which the patient complains of having bad breath but others are unable to detect it clinically through scientific testing. Delusional halitosis (also termed monosymptomatic hypochondriasis or imaginary halitosis) is a condition in which patients believe their breath is smelly and offensive, even in the absence of objective findings.
Halitosis affects approximately 25% of the world's population and has a large social and economic impact. Other reviews place the prevalence somewhat higher: the prevalence range has been reported at 22% to 50% in various populations. In most patients with halitosis, the condition causes embarrassment and interferes with social interactions and daily life, and bad breath can also be a sign of an underlying disease.
Halitosis is caused mainly by volatile sulfur compounds (VSCs) resulting from bacterial breakdown of protein, and can be quantitatively and qualitatively measured in expired oral breath. The methods of detecting or diagnosing halitosis are organoleptic (human sense of smell), sulfide monitoring, and gas chromatography — all of which have limitations and disadvantages. The organoleptic method performed by trained experts is considered the gold standard for diagnosing halitosis, but measurement of VSC levels using gas chromatography is objective and highly reliable.
Intraoral conditions, such as insufficient dental hygiene, periodontitis, and tongue coating, are considered to be the most important cause — accounting for approximately 85% — of halitosis. This malodor mainly results from the presence of odoriferous substances — named volatile sulfur compounds (VSCs) — present in the exhaled air as a result of the action of anaerobic oral Gram-negative bacteria (Bacteroides loescheii, Centipeda periodontii, Eikenella corrodens, Treponema denticola, Prevotella intermedia, Porphyromonas gingivalis, Fusobacterium nucleatum, Selenomonas, Eubacterium, and Tannerella forsythia) on substrates containing sulfur.
Hydrogen sulfide, methyl mercaptan, and, to a lesser extent, dimethyl sulfide represent approximately 90% of the VSCs in bad breath. Among VSCs, methyl mercaptan has the lowest odor threshold, followed by hydrogen sulfide and dimethyl sulfide; this means these substances are mainly responsible for the unpleasant smell in the mouth, and methyl mercaptan is perceptible at much lower concentrations than the other compounds.
VSCs are products of the metabolism of sulfur-containing amino acids — methionine, cysteine, and homocysteine — in Gram-negative anaerobic bacteria, with hydrogen sulfide and mercaptans as the principal end products. In addition to VSCs, other odorous substances in intraoral halitosis include aromatic compounds, amines, short-chain fatty or organic acids, alcohols, aliphatic compounds, aldehydes, and ketones.
In the oral cavity, the most relevant anatomical part related to intraoral halitosis is the tongue; the tongue-associated microbiota produce malodorous compounds and fatty acids. Tongue coating (TC) is a biofilm comprising desquamated epithelial cells, food debris, and microorganisms. Factors such as age, diet, smoking, and systemic conditions influence its formation, and TC is a primary reservoir for pathogenic bacteria closely linked to halitosis and periodontal disease.
The oral bacteria most closely related to halitosis are Actinomyces spp., Bacteroides spp., Dialister spp., Eubacterium spp., Fusobacterium spp., Leptotrichia spp., Peptostreptococcus spp., Porphyromonas spp., Prevotella spp., Selenomonas spp., Solobacterium spp., Tannerella forsythia, and Veillonella spp.
VSCs can be toxic for human cells even at low concentrations. Inflamed periodontal pockets in periodontitis provide a stable habitat for the oral microbiota, which enhances hydrogen sulfide production. Eighty to ninety percent of halitosis is caused by intraoral factors, with coated tongue, periodontal diseases, and poor oral hygiene practices being the principal factors.
Saliva plays a vital role in maintaining the health of hard and soft tissues in the oral cavity; it helps remove food debris, neutralize acids, and protect against bacterial infections, thereby preventing dental caries, periodontal disease, and mucositis. One of the primary symptoms associated with dry mouth is halitosis or bad breath, which arises due to decreased salivary flow and the subsequent build-up of bacteria in the oral cavity. Reduced salivary flow (hyposalivation) facilitates the formation of deposits on the tongue, promotes the onset of periodontal diseases and dental caries, decreases commensal populations in the oral cavity, and facilitates acquisition of periodontal pathogens, leading to oral dysbiosis and, in turn, intraoral halitosis.
Ear–nose–throat diseases account for approximately 10% of halitosis cases. Extra-oral halitosis originates from the nasal, paranasal, and laryngeal regions, the pulmonary or upper digestive tract, and bloodborne odors; approximately 3% of extraoral halitosis cases originate on the tonsils, due to caseum (tonsil stone) accumulation in their crypts — containing desquamated epithelial cells, keratin, and food debris colonized by anaerobic bacteria that produce VSCs. Bacterial sinusitis is the main cause of malodor exhaled through the nasal cavity.
Gastrointestinal causes account for most of the extraoral causes of halitosis; GI reflux, gastric and peptic ulcers, congenital broncho-esophageal fistula, Zenker's diverticulum, carcinoma of the stomach, hiatus hernia, pyloric stenosis, duodenal obstruction, and steatorrhea are among the recognized causes. Both Enterococcus faecalis and Helicobacter pylori have been found in periodontal spaces and can contribute to halitosis.
Metabolic diseases that can cause halitosis include diabetes, kidney failure, liver failure, trimethylaminuria, hypernatremia, and cystinosis. Certain endocrinological and metabolic disorders — such as diabetes mellitus — render a fruity or acetone-like odor to the breath, while in uremia the breath acquires an ammoniacal odor. Diabetes mellitus may produce acetone breath due to excretion of acetone through the lungs; a sweet odor sometimes described as that of "dead mice" has been associated with liver insufficiency; and a "fish odor" can suggest kidney insufficiency.
Metabolic disorders like trimethylaminuria (fish odor syndrome) are characterized by the presence of trimethylamine (TMA), whose odor resembles that of rotting fish in urine, sweat, and expired air; individuals with trimethylaminuria have diminished capacity to oxidize dietary-derived TMA to its odorless metabolite TMA N-oxide, resulting in increased excretion of large amounts of TMA in body fluids.
Multiple systemic conditions — including liver pathology, pre-kidney transplantation, renal pathology, viral hepatitis B infection — and certain food or medication products can cause bloodborne factors that lead to extra-oral halitosis.
In cases of use of chemotherapy drugs, acetaminophen, chloral hydrate, dimethyl sulfoxide, disulfiram, nitrates and nitrites, and phenothiazines, halitosis can be observed. Medications interfering with the neural control of salivary glands — such as cytotoxic drugs, anticholinergic drugs, proton pump inhibitors, psychoactive agents, sympathomimetic drugs, antihypertensives, and diuretics — are associated with dry mouth as a side effect, which in turn can worsen oral malodor.
Both self-assessed and clinical halitosis are statistically significantly associated with tongue coating, poor oral hygiene, gingival bleeding, periodontal pockets, caries, and imperfect restorations. The most consistently reported intraoral factors include coated tongue, higher saliva viscosity, and periodontal diseases with a higher number of bacterial species — particularly Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola. Periodontal disease-associated oral bacteria in tongue coatings are closely related to halitosis, and tongue cleaning may be an effective method for improving it.
Halitosis is among the major concerns in smokers: in a recent survey, 73% of smokers reported being afraid of developing this condition, and cigarette smokers have a higher measured and self-perceived incidence of halitosis than non-smokers. Multivariate analysis has identified smoking as an independent predictor of both self-assessed and clinical halitosis. Smoking can change the balance of microbes in the mouth, cause dry mouth, and increase the risk of oral health issues.
Avoiding a diet high in volatile foods, such as onions, garlic, and spices, can aid in the prevention of halitosis. The body absorbs chemicals from foods such as garlic and onions into the bloodstream, carries them to the lungs, and exhales them — creating a systemic (bloodborne) form of transient halitosis that is not primarily oral in origin. Breakfast consumption has been linked to a lower risk of halitosis.
Low-carbohydrate and ketogenic diets: Physiological causes of halitosis also include dehydration, starvation, and dry mouth. During ketogenic or very low-carbohydrate diets, the body increases fat oxidation, producing ketone bodies including acetone. Acetone is exhaled through the lungs, creating a characteristic fruity or acetone-like breath odor distinct from bacterially-generated VSC halitosis. CKD patients and others with elevated ketone states may experience heightened levels of volatile sulfur compounds such as hydrogen sulfide, methyl mercaptan, and dimethyl sulfide, which are linked to bad breath.
Different alcoholic beverages cause reduced salivation; they contain sugars that promote acid production in the oral cavity by pathogens that demineralize the enamel and damage gums and teeth. Chronic alcohol consumption can progress to different types of oral disorders, including halitosis and caries. Avoiding alcohol use is recommended because of its negative effects on bad breath.
Hyposalivation promotes the development of dental caries and eventual tooth loss, in particular when combined with poor oral hygiene and a diet rich in sugar and carbohydrates. Diseases affecting the salivary glands include autoimmune disorders like Sjögren's syndrome, endocrine conditions such as type I and II diabetes mellitus, thyroid disorders, and adrenal gland disorders, all of which can affect salivary gland function and reduce saliva production. Tobacco use — whether through chewing or smoking — increases the risk of dry mouth by affecting saliva production and quality, and dehydration caused by insufficient fluid intake can also contribute.
Two mechanisms of oral malodor inhibition by zinc ions have been identified: first, zinc ions have a strong affinity for the thiol groups present in VSCs, and they exhibit immediate inhibitory effects on VSC production by effectively and directly reducing VSC activity; second, zinc ions have an antibacterial effect. Zinc ions can reduce the expression of VSCs by binding to sulfur radicals, converting volatile H₂S and CH₃SH into non-volatile zinc-sulfides; neutralizing VSCs with zinc ions is more effective for immediate action, while reduction of microorganisms using the antibacterial properties of mouthwash is more effective for long-term action.
In a double-blind, crossover, randomized clinical trial involving 24 adults with halitosis, hydrogen sulfide (H₂S), methyl mercaptan (MM), and organoleptic scores were significantly reduced 12 hours following rinsing with all substances tested — including zinc acetate and chlorhexidine diacetate combinations — compared to placebo. All treatments resulted in reduction in halitosis 12 hours after rinsing compared to placebo, and H₂S and MM were most effectively reduced by zinc acetate and chlorhexidine diacetate.
Although these characteristics suggest zinc ions might be effective oral anti-malodor agents, the majority of studies conducted to date have been based on their clinical use in combination with other agents; therefore, the two mechanisms of action — chemical binding and antimicrobial property — have not been individually assessed, and the antimicrobial effects of zinc ions on microorganisms related to oral malodor require further study.
A systematic review of zinc chloride specifically found: four studies were included and these studies showed the antimicrobial efficacy and ability of zinc chloride to inhibit VSC production by oral bacteria; zinc chloride provides a solution by offering both an antibacterial property and the ability to neutralize VSCs that cause halitosis. Despite the effective antimicrobial property and neutralization of VSCs by zinc chloride, it is still unable to directly act on gaseous VSCs. Overall, the evidence for zinc-containing oral rinses is characterized in the literature as having a "weak" strength of recommendation, though these formulations have the most available evidence among anti-halitosis mouthwashes.
Green tea has been consumed in East Asia for thousands of years, with its origins in China, and has a long history of use as a beverage and in traditional medicinal practice. Originating from China, tea has a long history of use that spread across numerous countries over thousands of years and represents one of the most popular beverages in the world. Traditional Chinese and Japanese oral health practices have historically included the use of green tea for mouth cleansing.
Several studies have brought evidence that green tea polyphenols may be effective in reducing halitosis. In a saliva-putrefaction in vitro model, green tea strongly inhibited VSC production, and also demonstrated strong deodorant activity in vitro, leading researchers to conclude that green tea was very effective in reducing oral malodor temporarily because of its disinfectant and deodorant activities.
Laboratory investigation established that Solobacterium moorei is a VSC-producing Gram-positive anaerobic bacterium associated with halitosis, and researchers investigated the effects of green tea extract and its major constituent epigallocatechin-3-gallate (EGCG) on its growth and halitosis-related properties.
In a human randomized controlled trial, a parallel-arm double-blind RCT was conducted over 21 days with 90 adult participants randomized into three groups: saline, 5% Camellia sinensis mouth rinse, or 0.2% chlorhexidine mouth rinse; tongue coating and oral halitosis scores were recorded at baseline and after 21 days. The findings indicated that the green tea mouth rinse was equally effective in reducing plaque accumulation, tongue coating, and the severity of oral halitosis compared to the chlorhexidine control. Natural ingredients such as green tea powder also reduce oral malodor through various antibacterial mechanisms.
Evidence strength: The clinical evidence for green tea in halitosis is preliminary and based on small, short-duration trials. The in vitro and laboratory findings are more robust but not directly translatable to clinical practice without further large RCTs.
Probiotics, especially Lactobacillus species, have been proposed for the treatment of genuine halitosis, due to their ability to reduce bacterial colonization. The genera Lactobacillus, Streptococcus, and Weissella are among the most useful probiotics for the prevention or treatment of halitosis in the oral cavity.
A 2022 systematic review and meta-analysis found: probiotics such as Lactobacillus salivarius, Lactobacillus reuteri, Streptococcus salivarius, and Weissella cibaria may relieve halitosis in the short term (≤4 weeks), with organoleptic scores (SMD = −0.58) and VSC levels (SMD = −0.26) both decreasing significantly in the probiotic group compared to placebo; however, in the long term, only organoleptic score reduction remained significant. The results of bias assessment, limited data, and heterogeneity of included clinical trials might reduce the reliability of these conclusions.
An earlier meta-analysis reported: transient (average of 2 weeks) dosing with probiotics (mainly Lactobacillus strains) had a moderate effect on halitosis regarding organoleptic scores, but the authors could not confirm the effects of probiotics on VSC reduction.
A 2025 12-week double-blind RCT reported: a 12-week, randomized, double-blind, placebo-controlled clinical trial involving 80 participants (70 completing) investigated Complex OK oral probiotics containing Lactobacillus gasseri HHuMIN D and L. paracasei OK, with significant reductions in H₂S and total VSCs observed in the experimental group.
The long-term efficacy of probiotic therapy for halitosis remains unclear, as most clinical trials have focused on short-term outcomes (4 to 12 weeks); although meta-analyses and RCTs have demonstrated that several probiotics can significantly reduce VSC levels and improve organoleptic scores in the short term, evidence supporting sustained efficacy is limited, and future studies should incorporate extended follow-up periods.
Evidence strength: Moderate for short-term organoleptic improvement based on meta-analyses of RCTs; weak-to-moderate for VSC reduction; insufficient for long-term efficacy. Heterogeneity between trials (strains, doses, durations) limits firm conclusions.
Oil pulling is an ancient Ayurvedic procedure involving swishing oil in the mouth for oral and systemic health benefits; it is mentioned in the Ayurvedic text Charaka Samhita where it is called Kavala or Gandusha. Oil pulling involves swishing edible oil — typically sesame or coconut — throughout the mouth and between teeth, then expectorating; customary protocols specify continuous swishing for approximately 5 to 20 minutes before routine toothbrushing. Ayurveda is a form of traditional holistic medicinal system originating in the Indian subcontinent, with practice reportedly dating back some 3,000–5,000 years.
Oil pulling therapy using sesame oil was found to be as effective against halitosis and associated pathogens as chlorhexidine rinses, which are considered a gold standard, and is also more cost-effective than chlorhexidine with no associated side effects such as allergic reactions and mucosal staining following prolonged use. Oil pulling is believed to improve gingival health and bleeding by reducing inflammation, relieving dry mouth, whitening teeth, reducing bad breath, and improving oral hygiene.
Evidence strength: Preliminary. The available RCTs on oil pulling for halitosis are few, small, and often limited to short-term pilot designs. Current evidence does not support definitive clinical recommendations; more rigorous trials are needed.
Several plant-based materials have long-standing traditional use as breath fresheners across multiple cultures. Parsley has been used in European folk tradition as a breath freshener, attributed to its high chlorophyll content. Fennel seeds are traditionally offered after meals in South Asia to stimulate salivation and freshen breath. Cloves have a history of use in traditional Chinese and Ayurvedic medicine for oral health, attributed to their eugenol content.
In a saliva-putrefaction in vitro study, parsley-seed oil product could not inhibit saliva putrefaction, and no significant deodorant activity of parsley-seed oil product was observed. Deodorizing capsules containing chlorophyll have minimal evidence for bad breath in the clinical literature reviewed. A study investigating the effectiveness of Phyllanthus emblica (amla/Indian gooseberry) fruit extract demonstrated dose-dependent inhibition of halitosis-related bacteria — including Fusobacterium nucleatum and Porphyromonas gingivalis — while significantly lowering VSCs in clinical trials with a 5% mouthwash; the extract also exhibited anti-inflammatory effects by reducing markers like IL-6 and IL-8 in oral epithelial cells.
Evidence strength: For parsley and chlorophyll as oral deodorizers, the published evidence base is currently very weak to absent in clinical trials. The Phyllanthus emblica findings are early-stage and require replication. Traditional use of these agents is well-documented, but it has not been validated in high-quality RCTs.
Natural ingredients such as hinokitiol, green tea powder, and eucalyptus extract have been shown to reduce oral malodor through various antibacterial mechanisms. These findings are predominantly from in vitro and laboratory studies; large-scale human clinical trials specifically addressing eucalyptus and similar plant antimicrobials as standalone halitosis interventions are sparse in the peer-reviewed literature.
Glycyrrhizic acid and glycyrrhizin flavonoids in licorice have a good inhibitory effect on a variety of periodontal pathogens, and can help prevent dental diseases such as caries, periodontitis, gingivitis, candidiasis, and periodontitis. Licorice's role specifically in halitosis has not been well-characterized in dedicated clinical trials; the available evidence relates to its broader oral antimicrobial effects.
Eating foods such as onions and garlic is a common cause of bad breath; the body absorbs chemicals from these foods into the bloodstream, carries them to the lungs, and exhales them. This systemic mechanism distinguishes diet-related halitosis from the locally-generated oral form. Other physiological causes include dehydration, starvation, dry mouth, advanced age, and some types of food.
Saliva consists of water, proteins, and electrolytes that improve taste, speech, and swallowing, and facilitate irrigation, lubrication, and protection of the mucous membranes in the upper digestive tract. Saliva also provides antimicrobial (via mucin, histatins, lysozyme, and lactoferrin) and buffering activities that protect the teeth from dental caries. Hyposalivation promotes the development of dental caries and eventual tooth loss, in particular when combined with poor oral hygiene and a diet rich in sugar and carbohydrates. Maintaining adequate fluid intake is therefore considered a foundation for salivary health and oral malodor control, though systematic research specifically quantifying the halitosis-reducing effect of hydration alone is limited.
Breakfast consumption has been linked to a lower risk of halitosis in the reviewed literature. Fasting or extended periods without eating are recognized physiological contributors to transient morning halitosis, due to reduced salivary flow and increased bacterial activity during periods of low oral substrate availability.
The presence of tongue coating is related primarily to oral hygiene and less frequently to smoking, periodontal status, the presence of dentures, and dietary habits. Clinical evidence shows that use of tongue scrapers on a regular basis has a significant improvement in eliminating anaerobic bacteria and decreases bad odor.
One study in subjects with periodontitis found that VSC levels were higher in gingival pockets of smokers than non-smokers; in other studies, VSCs and organoleptic scores were significantly associated with both bacterial tongue coating and cigarette smoking.
Tongue coating formation is influenced by factors such as age, diet, smoking, and systemic conditions. It is a primary reservoir for pathogenic bacteria closely linked to halitosis and periodontal disease. Beyond oral health, tongue coating has been associated with systemic diseases — including aspiration pneumonia, cardiovascular disease, and diabetes — through mechanisms involving microbial translocation and low-grade inflammation.
Aloe vera mouthwash has been evaluated in clinical trials for its antibacterial and anti-inflammatory effects in the oral cavity, which are relevant to halitosis reduction. Its antiseptic constituents (salicylic acid, lupeol, sulfur-containing agents) suppress oral bacteria responsible for volatile sulfur compound production. It has also shown efficacy against oral candidiasis, a contributing factor to oral malodor.
Betel leaf has well-documented antimicrobial activity against oral pathogens responsible for halitosis. Chewing the leaf reduces oral microflora and is traditionally valued as a breath freshener. Scientific studies confirm inhibition of key odor-causing bacteria. A randomized clinical trial demonstrated significant plaque and gingival-bleeding reduction with betel leaf toothpaste.
A randomized, double-blind, placebo-controlled crossover trial found that black tea rinsing reduced volatile sulfur compound (VSC) levels associated with halitosis. Black tea polyphenols inhibit sulfur-producing oral bacteria. The effect was measured objectively using portable gas chromatography.
Carvacrol, the principal phenolic terpenoid of thyme and oregano essential oils, has documented in vitro antimicrobial activity against VSC-producing oral pathogens responsible for halitosis. It is an active constituent in thyme oil, which has been confirmed effective in a clinical RCT for halitosis improvement. Carvacrol inhibits biofilm formation by Streptococcus mutans and demonstrates activity against P. gingivalis and S. moorei relevant to halitosis.
Tea catechins—especially EGCG—reduce volatile sulfur compounds (VSCs) responsible for halitosis by inhibiting the anaerobic bacteria that produce them. Both in vitro and clinical evidence support this deodorizing action. Green tea mouthwash has been shown to reduce oral malodor in human studies.
Multiple human clinical trials, including a placebo-controlled double-blind RCT in 80 adults aged 50–79, demonstrate that oral champignon extract (50–1000 mg/day for 4 weeks) significantly reduces halitosis versus placebo. The mechanism involves inhibiting intestinal production of methyl mercaptan, ammonia, indole, and related malodorous compounds. Evidence is dose-dependent and reproducible across studies.
Cinnamon bark essential oil inhibits Solobacterium moorei, a bacterium directly associated with halitosis, suppressing its biofilm and hydrogen sulfide production. Cinnamaldehyde, the principal flavor compound, is among the most potent plant-derived agents against oral malodor bacteria. Evidence is currently in vitro, with no completed human RCTs specifically on halitosis as an endpoint.
Coconut oil pulling has been studied in a randomized controlled pilot trial for its effects on halitosis, showing reductions in odor-causing oral microorganisms. The antimicrobial properties of lauric acid reduce the bacterial load responsible for volatile sulfur compound production, which underlies bad breath.
Oil pulling with coconut oil has been evaluated in randomized controlled trials and shown to reduce salivary bacterial counts and plaque, both of which are associated with halitosis. A systematic review of four RCTs (n=182) found significant reductions in salivary bacterial colony count (p=0.03) with coconut oil pulling. Direct studies on halitosis endpoints are limited but results are consistent with plaque and bacterial load reductions.
EGCG, the principal catechin of green tea, directly neutralizes methyl mercaptan by chemical reaction and suppresses the mgl gene in Porphyromonas gingivalis that encodes the enzyme responsible for methyl mercaptan production. In vitro studies confirm EGCG inhibits growth and VSC production by multiple halitogenic bacteria including Solobacterium moorei and P. gingivalis. Research published in Journal of Dental Research (2010) confirmed bactericidal and mgl-suppressing effects at clinically relevant concentrations.
Eucalyptus extract and eucalyptol-containing mouthwashes and chewing gums have demonstrated significant reductions in volatile sulfur compounds (VSCs) and oral bacterial load in clinical studies. Eucalyptol is an active constituent of established therapeutic mouthwashes. A clinical study of eucalyptus-extract chewing gum showed long-term reduction in tongue coating score, organoleptic score, and VSC levels.
Eugenol, the principal active in clove oil, is a well-characterized antimicrobial used in clinical dentistry. It inhibits VSC-producing oral pathogens and is an active ingredient in commercial antiseptic mouthwashes including Listerine. A systematic review of essential oils for halitosis confirmed eugenol-containing oils exert documented antimicrobial effects against halitogenic bacteria. It is listed by systematic reviews and dental pharmacology sources among effective oral antiseptic agents.
Garlic is a well-characterized, mechanistically understood cause of halitosis rather than a remedy. Allyl methyl sulfide (AMS), produced during garlic metabolism, is absorbed into the bloodstream, excreted via the lungs, and causes characteristic breath malodor lasting hours to days. This is a scientifically validated adverse effect of garlic consumption.
Green tea catechins, particularly EGCG, inhibit VSC-producing bacteria and directly neutralize methyl mercaptan through chemical reaction with the EGCG B-ring. A systematic review of Camellia sinensis for halitosis found that green tea mouthwash reduced VSC concentrations, with one study showing it was as effective as 0.2% chlorhexidine in reducing halitosis. Clinical and laboratory research published in peer-reviewed journals supports these findings.
Honey's high osmotic pressure and antimicrobial properties can reduce oral bacteria responsible for volatile sulfur compound production, thereby improving halitosis. A 2021 clinical study in stroke patients found honey reduced halitosis scores, with honey outperforming chlorhexidine mouthwash. Ancient Egyptian texts from 1550 BCE also document honey in formulations for bad breath.
A randomized, double-blind, placebo-controlled trial tested L. brevis CD2 lozenges (4 tablets/day for 14 days) in 20 patients with active halitosis, using multi-sensor electronic nose technology alongside traditional odor assessment methods. L. brevis CD2 competes with volatile sulfur compound (VSC)-producing anaerobic bacteria in the oral cavity. Evidence is promising but trial sample sizes remain small and follow-up periods short.
Lactobacillus reuteri produces reuterin and reutericyclin, bacteriocins that inhibit VSC-producing gram-negative oral anaerobes. A randomized double-blind placebo-controlled crossover trial tested L. reuteri DSM 17938 and ATCC PTA 5289 via chewing gum in adults with morning halitosis. A 2022 meta-analysis confirmed L. reuteri as one of the strains showing short-term VSC reduction in halitosis subjects.
Lactobacillus rhamnosus inhibits the growth of Porphyromonas gingivalis, Prevotella intermedia, and Tannerella forsythia—primary VSC-producing bacteria responsible for halitosis. An in vitro microbiological study published in PMC (2023) confirmed L. rhamnosus inhibitory effects against these halitosis-causing bacteria. A 2021 comprehensive review confirmed mechanistic support for its role in reducing the pathogen load responsible for VSC generation.
Lactobacillus salivarius, particularly strain WB21, has been studied in RCTs for halitosis. A double-blind, randomized, placebo-controlled crossover trial found L. salivarius WB21 tablets significantly reduced organoleptic test scores and H2S, CH3SH, and total VSC concentrations in subjects with physiological halitosis. A 2022 meta-analysis identified L. salivarius as one of the strains with the strongest evidence for short-term VSC reduction.
Clinical trials show that lactoferrin/lactoperoxidase (LPO) combination tablets reduce volatile sulfur compound (VSC) levels in subjects with measurable oral malodor. A randomized, double-blind, crossover, placebo-controlled trial found suppressive effects on oral malodor with evidence of selective influence on oral bacteria. An in vitro and preliminary in vivo study also confirmed antibacterial activity of LPO-containing compositions and their effect on breath odor.
Lemongrass essential oil mouthwash has been shown in clinical studies to reduce oral malodor, partly through its action on periodontal pathogens that produce volatile sulfur compounds. A 2024 scoping review identified oral malodor reduction as a documented clinical effect of LGEO, with efficacy noted in periodontal patients.
Licorice root contains licoricidin and licorisoflavan A, which have been demonstrated in published research to reduce bacterial VSC production relevant to halitosis. A study published in the Journal of Breath Research (Tanabe et al., 2012) confirmed that licoricidin and licorisoflavan A from licorice reduced VSC production by halitogenic bacteria. Glycyrrhizin and other licorice constituents also have antimicrobial activity against oral pathogens.
Magnolia bark extract (MBE) demonstrates strong antimicrobial activity against oral bacteria responsible for halitosis. In a controlled human volunteer study, mints containing MBE killed over 61% of bad-breath-causing bacteria within 30 minutes versus only 3.6% for plain mints. Magnolol and honokiol show bactericidal action against Fusobacterium nucleatum and other sulfur-compound-producing species.
A clinical study in 60 gingivitis patients found that a herbal mouthwash containing mangosteen pericarp extract significantly improved volatile sulfur compound (VSC) levels—the primary chemical cause of halitosis—compared to placebo. MSKCC cites this clinical evidence for halitosis control. The antibacterial activity of xanthones against oral bacteria provides a plausible mechanism.
Multiple randomized clinical trials demonstrate that mastic gum formulations (toothpaste, mouthwash) reduce volatile sulfur compounds (VSCs), the primary chemical drivers of halitosis. A 2025 double-blind RCT showed mastic toothpaste significantly reduced hydrogen sulfide (H2S) levels from ~221 ppb to ~125 ppb in orthodontic patients over 14 days. A 2023 RCT similarly found mastic mouthwash reduced VSC levels versus placebo.
Melaleuca alternifolia (tea tree) essential oil inhibits VSC-producing bacteria associated with halitosis including Solobacterium moorei, Porphyromonas gingivalis, and Porphyromonas endodontalis. In vitro studies confirm hydrogen sulfide production is reduced. A clinical study in ICU patients using a TTO-containing mouthwash showed significant reductions in oral malodor and VSC levels. Research from the University of Basel's Institute of Preventive Dentistry substantiated these antimicrobial effects.
Menthol is a recognized antimicrobial component in oral rinse formulations used to reduce halitosis-causing bacteria. The American Dental Association acknowledges essential oil mouthrinses containing menthol for reducing plaque and controlling bad breath. Evidence is primarily from clinical use of multi-ingredient essential oil formulations.
Peppermint oil and mouthrinses containing mint have been tested in clinical trials for halitosis reduction, showing antibacterial activity against halitosis-associated bacteria such as Fusobacterium nucleatum and measurable reductions in organoleptic scores. Menthol also provides a masking sensory effect.
TC mouthwash demonstrated significant reductions in microbial plaque and salivary pH normalization in a 2-week clinical trial, both of which directly impact oral malodor. Its potent antibacterial activity against oral bacteria, including Streptococcus mutans, further supports efficacy for halitosis.
Neem twigs and bark have a documented role as oral deodorants in traditional medicine, and this is supported by clinical studies showing neem mouthwashes reduce the oral bacterial load responsible for volatile sulphur compounds causing halitosis. The PMC dental review confirms that frequent use of neem-containing mouthwash lessens gingival problems and treats halitosis.
Oregano essential oil (OEO) has been evaluated in a clinical study comparing it to chlorhexidine mouthwash for halitosis. OEO mouthwash demonstrated results similar to chlorhexidine in reducing oral malodor, assessed by organoleptic method and the BANA test. The antimicrobial activity against odor-causing oral bacteria, including S. mutans and anaerobes, underpins this effect. Carvacrol is the primary active constituent responsible.
Peppermint oil and peppermint mouthwash have been clinically studied for halitosis. A published RCT in girls with confirmed halitosis found peppermint mouthwash significantly more effective than placebo after one week of use. A comparative clinical trial in 88 dental students confirmed that peppermint mouthwash reduced organoleptic halitosis scores over a 21-day protocol. Peppermint's antimicrobial constituents, including menthol, inhibit VSC-producing oral anaerobes.
Pomegranate-based mouthwashes and peel extracts have been evaluated in clinical studies for antimicrobial effects against halitosis-causing oral bacteria. Pomegranate exhibits significant inhibitory activity against Fusobacterium nucleatum, Porphyromonas gingivalis, and other anaerobes responsible for VSC-producing oral biofilms. Several RCTs have compared pomegranate mouthwash to chlorhexidine.
Sesame oil oil-pulling has been studied in clinical trials and found comparable in efficacy to chlorhexidine rinse for reducing halitosis and associated odor-producing bacteria. A 2014 RCT (J Clin Diagn Res) and an RCT pilot trial (J Indian Soc Pedod Prev Dent, 2011) support this. The mechanism involves mechanical removal of bacteria and saponification of microbial cell membranes during swishing.
Streptococcus salivarius, particularly strain K12, is the most clinically studied oral probiotic for halitosis. It produces bacteriocins (salivaricin A2 and salivaricin B) that suppress VSC-producing bacteria. A preliminary study (Burton et al.) found that 85% of K12-treated subjects vs. 30% of placebo had >100 ppb VSC reductions. Multiple systematic reviews confirm S. salivarius K12 reduces VSC levels and organoleptic scores in halitosis subjects.
Oil pulling with sunflower oil is documented to reduce oral microbial burden and plaque, both causally linked to halitosis. A PMC review of oil pulling notes that at least three separate clinical trials found oil pulling reduces bacteria responsible for halitosis. Sunflower oil has been specifically used in oil-pulling studies showing reduced oral bacterial load.
Tea tree oil (Melaleuca alternifolia) has been studied for halitosis due to its antimicrobial terpenoids, particularly terpinen-4-ol, which inhibit VSC-producing bacteria such as Solobacterium moorei, Porphyromonas gingivalis, and Porphyromonas endodontalis. A clinical study in ICU patients using an essential oil solution containing tea tree oil showed significant reductions in oral malodor and VSC levels. Laboratory research at the University of Basel confirmed tea tree oil reduces hydrogen sulfide production by oral bacteria.
Thyme (Thymus vulgaris) contains thymol and carvacrol, potent antimicrobials with documented activity against VSC-producing oral pathogens. A published RCT found that thyme mouthwash after periodontal treatment was effective in improving bad breath and gingivitis in gingivitis patients. Traditional use of thyme for oral malodor is well documented across Mediterranean and Moroccan ethnobotany.
Multiple randomized controlled trials show Triphala mouthwash significantly reduces oral bacterial colony counts, a key driver of halitosis. Its broad-spectrum antimicrobial activity against oral pathogens is well-documented. Human clinical evidence supports its use as an antibacterial oral rinse comparable to chlorhexidine.
Methyl salicylate from wintergreen oil is listed by the American Dental Association as an antimicrobial component in therapeutic mouthrinse formulations used for bad breath control. Its antimicrobial properties target odor-causing oral bacteria. Wintergreen is used as a flavoring and antimicrobial agent in mouthwashes and breath products.
Zinc ions directly neutralize volatile sulfur compounds (VSCs), the primary cause of halitosis, by binding to sulfur moieties and rendering them odorless. Multiple randomized controlled trials using zinc lactate, zinc acetate, and zinc chloride mouthwashes have demonstrated significant reductions in oral VSC levels and organoleptic scores compared to placebo. A 2021 single-blind crossover RCT (n=60) confirmed zinc lactate mouthwash combined with tongue scraping significantly reduced morning breath VSC concentrations (p<0.05).
Activated charcoal has been used in traditional and folk medicine as an oral deodorant and in some traditional dental powders to adsorb odorous compounds from the mouth. It is included in some modern toothpaste and oral care products marketed for bad breath. Activated charcoal is a potent non-specific adsorbent; while its internal use for systemic deodorization has limited modern evidence, topical oral application for adsorbing VSC molecules has traditional support and mechanistic plausibility.
Ajwain seeds are traditionally chewed after meals as a mouth freshener and remedy for bad breath across South Asian cultures. Thymol, the principal volatile compound, is a recognized antiseptic used in commercial mouthwashes. In vitro antimicrobial studies support activity against oral pathogens, but no human trials have assessed ajwain specifically for halitosis.
Galangal root extract has traditionally been used as a mouthwash and gargle in several herbal systems to combat bad breath and oral inflammation. This use is grounded in its documented antimicrobial activity against oral pathogens. No controlled clinical trials specifically targeting halitosis have been published.
Anise (Pimpinella anisum) has been used since antiquity in Greek, Roman, Arabic, and European traditional medicine as a breath freshener and digestive. Traditional texts including Dioscorides document anise for sweetening breath. In Moroccan and Mediterranean traditional medicine, anise seeds are chewed or prepared as mouthwash decoctions for oral malodor. Anethole, the primary volatile, has documented antimicrobial activity against oral bacteria.
Basil leaves have a long folk-medicine history as a mouth freshener across multiple cultures. The antimicrobial volatile oils in basil (linalool, eugenol) inhibit oral bacteria responsible for halitosis in vitro. No dedicated human clinical trials for halitosis specifically have been published, but the antimicrobial oral data supports a plausible mechanism.
In Ayurvedic practice, belleric myrobalan fruit powder has traditionally been used as a tooth powder to reduce gum pain and bad breath. This use is documented in classical texts and ethnobotanical records but lacks dedicated clinical trial evidence. The antimicrobial activity of its tannins and gallic acid against oral pathogens provides a plausible mechanistic rationale.
Caraway seeds have traditional use as a breath freshener and to mask bad breath. The Mahboubi 2018 review specifically notes that caraway fruits are used as a 'popular remedy to mask alcoholic breath.' Antimicrobial properties of carvone against oral pathogens may provide a pharmacological basis.
Cardamom (Elettaria cardamomum) has been used across South Asian, Middle Eastern, and Scandinavian traditional medicine as one of the most well-known breath fresheners. In Ayurveda it is prescribed specifically for oral malodor. Its volatile components (1,8-cineole, α-terpinyl acetate) have antimicrobial activity against oral bacteria. Cardamom pods are traditionally chewed after meals in South Asia and the Middle East specifically to freshen breath.
Chlorophyll has been used as an internal deodorant for bad breath since at least the 1950s, when Dr. F. Howard Westcott reported anecdotal reductions in oral and body odor. Modern clinical reviews find no convincing controlled evidence that oral chlorophyll or chlorophyllin produces meaningful reductions in volatile sulfur compounds causing halitosis. The practice persists as a traditional remedy, and chlorophyll-based breath products remain commercially available in Europe and elsewhere.
Chlorophyllin has a long history of use as an internal deodorant dating to the 1950s, with early case reports supporting reduction of fecal and body odors in ostomy and incontinent patients. A small controlled trial (n=12) in Japanese trimethylaminuria patients showed significant reduction in urinary trimethylamine on 60 mg three times daily for 3 weeks. However, a placebo-controlled trial of chlorophyllin for colostomy odor found no significant benefit, and modern reviews note insufficient evidence for general halitosis.
Clove (Syzygium aromaticum) is one of the most documented traditional remedies for oral malodor across multiple cultures including Moroccan, Ayurvedic, and Middle Eastern traditional medicine. Its primary active compound eugenol has potent antimicrobial activity against oral pathogens. A PMC-indexed ethnobotanical survey documented Syzygium aromaticum as prescribed by 17.5% of traditional Moroccan healers for halitosis. Eugenol-based products are widely used in commercial dental applications.
Commiphora myrrh (myrrh) has a long-documented traditional use for halitosis via its antimicrobial and astringent action on the oral cavity. Commission E and ESCOP both recognize topical myrrh for oral and mucosal conditions. No dedicated halitosis RCTs have been identified.
Fennel (Foeniculum vulgare) seeds are traditionally chewed after meals across Indian, Middle Eastern, and Mediterranean cultures specifically to freshen breath, a practice dating over 2000 years. In Ayurveda, fennel is a primary mukhavasa (after-meal mouth freshener) specifically for halitosis. Its principal volatile anethole has antimicrobial properties. Indian mukhwas (mouth freshener) traditions feature fennel prominently.
Goldenseal is traditionally used as a mouthwash and oral rinse for bad breath, based on its antimicrobial action against oral bacteria and its astringent effect on oral mucosa. No clinical trials have evaluated goldenseal specifically for halitosis.
In Ayurvedic tradition, H. spicatum is described as an odour neutralizer (dur-gandhanashana) and is listed among traditional indications for treating foul breath. The systematic review by Rawat et al. (2018) in the Journal of Pharmacy and Pharmacology documents traditional use for 'foul breath.' No controlled clinical studies have assessed this use.
Lemon has been widely used traditionally to combat bad breath due to its acidic, antibacterial properties and ability to stimulate saliva production. The citric acid may inhibit oral bacteria responsible for volatile sulfur compound production, but clinical trial evidence for lemon-specific halitosis reduction is absent.
Myrrh (Commiphora species) has been used in traditional Middle Eastern, Ayurvedic, and European herbal medicine as an oral antiseptic and breath freshener for millennia. Traditional dental preparations incorporating myrrh were used to treat oral malodor and gum disease. A systematic review of essential oils for halitosis (Eur J Oral Sci 2020) confirmed myrrh essential oil has demonstrable antimicrobial activity against Solobacterium moorei and halitogenic bacteria, though with higher MIC values than leading essential oils.
Parsley (Petroselinum crispum) is one of the most widely recognized folk remedies for bad breath, used across European and Middle Eastern traditions. It has been recommended for combating garlic breath specifically. Parsley contains chlorophyll and volatile oils including apiol and myristicin with deodorizing properties. Modern research supporting parsley for halitosis is mechanistically plausible but formal clinical RCT evidence is limited.
Peach is explicitly listed as 'antihalitosis' in multiple traditional botanical references. This is attributed to the leaves or preparations of the tree, though the specific mechanism and preparation are not elaborated in surviving documentation.
Propolis is a resinous beehive product used in traditional medicine across many cultures for oral antisepsis and breath improvement. It contains flavonoids, phenolic acids, and caffeic acid esters with documented antimicrobial activity against oral pathogens. Traditional use for halitosis is documented in Middle Eastern, Eastern European, and Brazilian folk medicine. Some in vitro studies confirm propolis inhibits Streptococcus mutans and other oral anaerobes relevant to bad breath.
Sage (Salvia officinalis) has been used in European and Mediterranean traditional medicine as a mouthwash for halitosis, gingivitis, and oral infections. It contains rosmarinic acid, thujone, cineole, and other antimicrobials active against oral pathogens. A Moroccan ethnobotanical survey on traditional halitosis management documented sage among plants prescribed by traditional healers. A systematic review of essential oils for halitosis noted sage essential oil's antimicrobial activity against halitogenic bacteria.
Spearmint leaf (Mentha spicata) is one of the most universally used traditional breath-freshening herbs across European, Middle Eastern, and Asian cultures. It contains carvone and limonene with antimicrobial activity against oral pathogens. It is a primary ingredient in commercially available oral care products for bad breath. Direct clinical RCT evidence for dried spearmint leaf specifically for measured halitosis reduction is limited, placing its primary evidence in the traditional category.
Traditional use of A. calamus for bad breath and oral hygiene is documented in Unani and Ayurvedic traditions, attributed to its aromatic antimicrobial essential oil. The rhizome is used to 'treat mouth ulcers by preventing bleeding of the gums and bad breath' in Siddha and Unani systems.
Thymol from Thymus vulgaris is an active ingredient in commercial mouthwashes (including Listerine) and is used as an oral antiseptic to combat the bacteria responsible for bad breath. The ESCOP monograph recognises thyme as a traditional mouthwash for oral inflammation and bad breath. This use is supported by in vitro antimicrobial data but lacks dedicated clinical trials specifically for halitosis.
Wheatgrass juice has a longstanding traditional use for halitosis, attributed to the antibacterial and deodorizing properties of chlorophyll. JPTCP and naturopathic sources document this use. No clinical trial has evaluated wheatgrass for halitosis.
Go back