IngredientsColloidal silver consists of tiny silver particles in a liquid. More precisely, colloidal silver is a solution of water that contains nanometer-sized particles of silver. The silver content of the solution is expressed as milligrams of silver per one liter of water (mg/L) or parts per million (ppm), and the silver content is in the form of suspended particles divided into two forms: silver nanoparticles and ionic silver.
Silver is a metallic element (chemical symbol Ag, from the Latin argentum) with atomic number 47. It has no known biological role as an essential nutrient in humans. Silver is a metallic element that is mined as a precious metal. It has various industrial uses — for example, in jewelry, silverware, electronic equipment, dental fillings, photographic processing, and disinfecting water. People are commonly exposed to silver, usually in tiny amounts, through the environment (such as the air), drinking water, and food, and possibly their work or hobbies. Silver has no known biological function in living organisms.
The physical and chemical parameters of commercial colloidal silver products vary considerably. The most critical physico-chemical parameters that affect the antimicrobial potential of silver nanoparticles (AgNPs) include size, shape, surface charge, concentration, and colloidal state. The silver nanoparticles in colloidal solutions are typically spherical, with particle sizes ranging between 10 and 250 nm; analysis has shown that silver nanoparticles in colloidal solution may have a diameter of approximately 50 nm.
Common forms and preparations include:
The metal has been used in many configurations, including vessels or containers for liquid, coins, shavings, foils, sutures, solutions (e.g., nitrate, oxide, bromide, chloride, and iodide), colloids providing fine particles, and electric colloids (introduced in 1924, which provide even smaller particles of 0.1 mcm to 0.001 mcm in diameter).
The medicinal use of silver is not a new idea. Silver ion has been employed as an antimicrobial for several millennia, the discovery of this indication preceding modern science. Over millennia, silver has been used for numerous medical conditions, mostly empirically, before the realization that microbes were the agents of infection.
Herodotus, the Father of History, accounts that no Persian king, including Cyrus, would drink water that was not transported in silver containers, which kept the water fresh for years. This was particularly important in military conflicts, where fresh water from natural sources was not readily available. Greeks and Romans used silver vessels to store water, wine, and vinegar, recognizing silver's ability to keep liquids fresh and prevent spoilage. Silver plates and foils were also applied to wounds to promote healing and prevent infections.
Hippocrates, the man credited as being the father of medicine, taught that silver could help wounds heal and prevent illness. Silver was thought to purify the blood, prevent heart palpitations, and treat offensive breath. Modern uses of silver began to emerge in the 1500s, with silver nitrate used to chemically cauterize wounds. Silver nitrate was also used internally to treat brain infections, but this practice is no longer in use.
In Ayurvedic medicine, silver is used in small amounts as a tonic, elixir, or rejuvenating agent for patients debilitated by age or disease. In Ayurveda, silver is used in the form of Bhasma named as Rajat Bhasma or Chandi Bhasma, reportedly for 5,000 years. Bhasmas are very fine Ayurvedic medicinal powders prepared by the process of calcination of metals, gems, or minerals — the heating of solids to a high temperature for the purpose of removing volatile substances and converting them into oxides. Bhasmas are manufactured through a series of preparation methods that include detoxification of raw materials, crushing them with herbal juices, making small pieces, drying, and heating, with the end product being residues of metals and minerals.
Not until the late 1800s did Western scientists rediscover what had been known for thousands of years — that silver is a powerful germ fighter. Medicinal silver compounds were then developed, and silver became commonly used as a medicine. By the early part of the 1900s, silver as an antibacterial substance was becoming widespread.
Crede, a surgeon, is credited with being the first to employ colloidal silver for wound antisepsis in 1891, after observing Halsted applying silver foil to wounds to treat infections. Topical application of silver salts became a common therapy. Crusius used silver nitrate for the treatment of burn injuries in the 1890s, well before its recent rediscovery.
Colloidal silver was used to disinfect hospital equipment as well as to control infections through wound application, eye drops, nose drops, and intravenous injection. Prior to the introduction of modern antibiotics, colloidal silver was used as a germicide and disinfectant. With the development of modern antibiotics in the 1940s, the use of silver as an antimicrobial agent diminished.
Prior to the establishment of the Germ Theory of disease, the use of silver for medicinal purposes was based on folklore or tradition. The rediscovery of silver for medicinal uses prompted exaggerated claims by both proponents and detractors of silver therapy. The Internet has only added to the confusion. Oral colloidal silver solutions, although outlawed by the U.S. Food and Drug Administration, are still advocated, advertised, and available over the Internet.
The antibacterial action of silver is dependent on the silver ion. The effectiveness of silver compounds as an antiseptic is based on the ability of the biologically active silver ion (Ag⁺) to irreversibly damage key enzyme systems in the cell membranes of pathogens. Colloidal silver therefore acts through two principal chemical species — particulate metallic silver (AgNPs) and released ionic silver (Ag⁺) — whose relative contributions vary by formulation and biological environment.
Given the substantial fraction of ionic silver (Ag⁺) resident in as-supplied colloidal silver products as detected by ICP-MS, and the very limited gastrointestinal absorption of metallic nanoparticles of similar size in other studies in rodents, the silver detected in patient blood samples is predominantly ionic, with no evidence that intact silver nanoparticles are either absorbed into circulation through the human digestive tract or attached to blood components. The silver detected in serum in human subjects is first solubilized from ingested colloidal form in the upper gastrointestinal tract and absorbed into blood in ionic form.
Although significant progress has been achieved on the elucidation of the antimicrobial mechanism of silver nanoparticles, the exact mechanism of action is still not completely known. Current literature proposes multiple, overlapping mechanisms. Four primary bactericidal mechanisms of colloidal silver are highlighted in the literature: (i) bacteriolysis, triggering the destruction or dissolution of cellular membranes; (ii) generation of reactive oxygen species (ROS) and free radicals; (iii) destabilization of intracellular structures (e.g., mitochondria or ribosomes) and biomolecules (e.g., DNA and proteins); and (iv) modulation of signal transduction pathways. These mechanisms could be attributed to either silver nanoparticles or cationic silver, despite their different chemical and physical structures.
AgNPs possess broad-spectrum biocidal potential against bacteria, fungi, viruses, and Mycobacterium, in addition to exhibiting synergistic effects when combined with certain antibiotics. The mechanisms underlying antimicrobial action include the generation of oxygen-reactive species, damage to DNA, rupture of bacterial cell membranes, and inhibition of protein synthesis.
The effectiveness of silver ions and AgNPs against gram-positive and gram-negative bacterial cells has been reviewed, suggesting different modes of action. Gram-negative bacteria were found to be more prone to silver ions, whereas initial evidence would suggest that AgNPs display a superior penetration ability into gram-positive bacteria.
When bonded, silver nanoparticles cause their antibacterial cascade by interfering with the cell membrane and membrane transport system, hampering the cellular apparatus, inducing an increase in reactive oxygen species, and disrupting cell signaling. They also intercalate with purine and pyrimidine base sets of nucleic acids, irritating the hydrogen bond between parallel strands and leading to DNA denaturing.
AgNPs exert their antibiofilm activity by interacting with the protein, nucleic acid, polysaccharide, and lipid components of the extracellular polymeric substance (EPS). Wound healing is a complex biological process involving haemostasis, inflammation, cellular proliferation, and remodelling. The use of silver nanoparticles in wound care has gained significant attention due to their potent antimicrobial, anti-inflammatory, and tissue-regenerating properties. This use focuses on mechanisms of action, efficacy, and clinical applications, with the antimicrobial activity of AgNPs helping prevent infections in both acute and chronic wounds, while their ability to modulate inflammation and promote angiogenesis accelerates tissue repair.
Numerous studies have reported that combining antibiotics such as ampicillin, kanamycin, chloramphenicol, enoxacin, neomycin, and tetracycline with silver ions and AgNPs, either conjugated or co-administered, can significantly enhance the antimicrobial activity of both compounds to treat bacteria, even when silver and antibiotics alone exhibited limited antimicrobial activity.
Confusion about the difference between an antibiotic and an antiseptic has led to an enormous number of false claims regarding silver's benefits. There is no reliable evidence that colloidal silver benefits any health condition. The U.S. Food and Drug Administration issued a final rule establishing that all over-the-counter (OTC) drug products containing colloidal silver ingredients or silver salts for internal or external use are not generally recognized as safe and effective and are misbranded. The FDA issued this final rule because many OTC drug products containing colloidal silver ingredients or silver salts were being marketed for numerous serious disease conditions and the FDA was not aware of any substantial scientific evidence that supports the use of OTC colloidal silver ingredients or silver salts for these disease conditions.
Adequate safety and effectiveness data have not been provided to establish general recognition of the safety and effectiveness of colloidal silver or silver salt ingredients for any OTC drug uses. The data submitted did not include the required absorption, metabolism, tissue distribution, accumulation, excretion, and pharmacodynamics of silver in the body, both when taken internally and applied externally, and of the effect of the particle size of the silver on these systemic effects.
Evidence strength: No reliable clinical evidence supports oral colloidal silver for the treatment or prevention of any disease.
A few studies have evaluated the effectiveness of colloidal silver nasal spray to treat chronic sinus infections, but they did not demonstrate meaningful improvements. The most notable human trial is a randomized crossover study published in 2017. A prospective cohort study was conducted using a convenience sample of 20 randomized patients with recalcitrant chronic rhinosinusitis without polyposis (CRSsP). Colloidal silver, a widely used naturopathic agent, had recently shown anti-biofilm properties both in vitro and within a rhinosinusitis animal model. To date at the time of publication, no trials involving humans had been published in world literature. The purpose of the study was to assess the efficacy of CS as a topical nasal spray in patients with refractory CRSsP. A formal sample size calculation was not performed as no previous studies for intranasal colloidal silver were available. This was a pilot study and 20 participants were enrolled to examine safety, tolerance, and possible trends for consideration of a more formal randomized clinical trial.
A further study published in Frontiers in Microbiology in 2018 (Ooi et al.) also examined topical colloidal silver for recalcitrant CRS in a small clinical population. Emerging evidence showed that colloidal silver nanoparticles may be effective for reducing biofilms, and a randomized, double-blinded, placebo-controlled clinical trial was proposed to evaluate the effectiveness and safety of intranasal colloidal silver nanoparticles in adult patients with chronic rhinosinusitis.
Evidence strength: Preliminary. Pilot-level data only; small sample sizes; no definitive demonstration of meaningful clinical benefit in controlled trials to date.
It is important to note a distinction here between oral colloidal silver supplements and silver-based topical medical products. Silver remains valued in wound care, with evidence-based success in dressings, coatings, and medical devices (e.g., catheters, burn dressings). These uses involve topical or implanted silver nanoparticles used in minute amounts and regulated, and are not ingested orally.
The use of silver nanoparticles in wound care has gained significant attention due to their potent antimicrobial, anti-inflammatory, and tissue-regenerating properties. Reviews provide a comprehensive analysis of the role of AgNPs in wound healing, focusing on their mechanisms of action, efficacy, and clinical applications. The antimicrobial activity of AgNPs helps prevent infections in both acute and chronic wounds, while their ability to modulate inflammation and promote angiogenesis accelerates tissue repair.
A 2024 randomized open-label parallel clinical trial (Pathi et al., published in Cureus) examined topical silver nanoparticle formulations in wound infection: The study allocated 86 participants with infected wounds (culture-positive) into a silver nanoparticle-based cream arm (n=43) and a Mupirocin arm (n=43), documenting swab culture on day 5 and wound healing at day 28, along with periodic wound status using the Bates-Jensen Wound Assessment Tool. Patients also received oral/systemic antibiotics and other medications for underlying diseases. This design limits isolation of the silver nanoparticle effect.
Evidence strength: Topical silver nanoparticle wound care products have a stronger, regulated evidence base than oral colloidal silver supplements. However, these are distinct from orally consumed colloidal silver products sold as dietary supplements, and are generally separately regulated as medical devices or prescription topicals in many jurisdictions.
There is no clinical evidence supporting the use of colloidal silver to prevent or treat COVID-19. Furthermore, no alternative remedies or dietary supplements have been shown to prevent or cure COVID-19. The FDA and the Federal Trade Commission have taken action against a number of companies for making misleading claims about colloidal silver products in the context of COVID-19 claims.
Laboratory (in vitro) studies have investigated the antiviral properties of silver nanoparticles against various viruses, but these have not been translated to human clinical data for oral colloidal silver products.
Evidence strength: No human clinical evidence. In vitro antiviral data exist but have not been validated in clinical trials.
Colloidal silver, which has been claimed to be helpful for hepatitis C, is not safe; it can cause irreversible side effects. No clinical evidence supports its use for this condition.
Recent studies have highlighted the effectiveness of AgNPs against various clinically relevant bacterial strains through their potential to combat antibiotic-resistant pathogens. Studies have also shown the potential of AgNPs in curbing antibiotic-resistant bacterial strains. However, these findings remain largely in vitro or in animal models; there is insufficient human clinical evidence to support oral colloidal silver as an effective treatment for antibiotic-resistant infections.
Evidence strength: Preclinical (in vitro and animal model) data are promising, but no controlled human clinical trials confirm efficacy of oral colloidal silver against antibiotic-resistant infections.
Colloidal silver has been associated — whether by traditional claim, marketing, or preliminary scientific investigation — with the following body systems and health areas. The quality of evidence for each association varies widely:
A landmark human pharmacokinetics study examined 60 healthy volunteers through several time-length exposures to orally dosed commercial silver nanoparticles in a prospective, placebo-controlled, single-blind, dose-monitored, cross-over design. The study was the first to quantitate changes in human metabolic, hematologic, and sputum morphology, and to monitor for changes in physical findings and organ imaging after exposure to a commercially available aqueous silver colloid nanoparticle oral formulation.
To investigate whether an orally ingested commercially available colloidal silver nanoproduct produces pharmacokinetic interference on select cytochrome P450 enzymes, a prospective, single-blind, controlled in vivo human study using simultaneous administration of standardized probes for P450 enzyme classes CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4 was conducted. Oral ingestion of a commercial colloidal silver nanoproduct produces detectable silver in human serum after 14 days of dosing.
Silver retention was found to be 18% of an orally administered dose using a radioactive tracer in one investigation. After oral administration, when ionic silver and nanoparticulate silver were compared, the latter was shown to be less bioavailable based on higher faecal excretion and lower absolute levels in organs.
The transition to a soluble colloidal form increases the bioavailability of silver and also enhances its toxicity. Therefore, special attention should be paid to stable solutions of silver nanoparticles coated with a hydrophilic stabilizer.
Scientific studies have documented a variety of adverse effects linked to prolonged exposure to silver nanoparticles, including bioaccumulation in internal organs such as the liver, spleen, kidneys, and brain, as well as oxidative stress, mitochondrial dysfunctions, DNA damage, and gene expression alterations.
There is no established safe or therapeutically effective oral dose for colloidal silver as a dietary supplement, and no recommended daily intake has been set by any major regulatory or health authority. The following dosages are reported descriptively from the scientific literature and regulatory documents only:
The FDA issued a final rule establishing that all over-the-counter (OTC) drug products containing colloidal silver ingredients or silver salts for internal or external use are not generally recognized as safe and effective and are misbranded. This ruling took effect on September 16, 1999 (21 CFR 310.548).
There is a lack of adequate data to establish general recognition of the safety and effectiveness of colloidal silver ingredients or silver salts for OTC use in the treatment or prevention of any disease. Any OTC drug product containing colloidal silver ingredients or silver salts that is labeled, represented, or promoted for the treatment and/or prevention of any disease is regarded as a new drug within the meaning of the Federal Food, Drug, and Cosmetic Act, for which an approved application or abbreviated application is required for marketing.
A product not intended for OTC drug use would not be subject to this final rule. A product containing silver could, under certain circumstances, be marketed as a dietary supplement if it meets the statutory definition and other applicable requirements. Among other things, such a product's label must state that the product is a dietary supplement and meet other labeling requirements.
The Therapeutic Goods Administration (TGA) of Australia does not recognize colloidal silver as an effective oral therapeutic and has issued alerts regarding its potential toxicity.
Colloidal silver can cause serious side effects. The most common is argyria, a build-up of silver in the body's tissues causing a bluish-gray discoloration of the skin, which is usually permanent.
Argyria is a condition characterized by pigmentary changes secondary to exposure to silver salts and its accumulation in skin, mucous membranes, and annexes, which typically produces blue or gray-blue spots. The hyperpigmentation of argyria is usually permanent, and it follows a sun-exposed distribution.
A case of argyria in a 73-year-old male following ingestion of colloidal silver as an alternative medicine over 5 years was documented. He had a diffuse, slate-gray discoloration of his face and hands. A biopsy specimen from the face revealed brown-black extracellular granules in the upper dermis and between collagen bundles. Silver particles were also found in the mucosa of the colon.
There are recent reports of argyria resulting from the use of colloidal silver products that are readily available via the Internet. Many consumers use the Internet to obtain health information and make decisions about their treatment. Most reports of generalized argyria are related to colloidal silver intake, with approximately 15 reports in the literature at the time of one review. Uncertainty about the safe dosage of silver, together with the lack of insight of dietary supplements, exacerbates the problem.
It is not clear how much colloidal silver a person can take before it may be harmful. It can build up in the body's tissues over months or years. This can lead to a blue-gray tint on skin, eyes, organs, nails, and gums — a condition called argyria. Argyria does not typically cause a major health problem, but it can be a cosmetic concern because it does not go away when silver products are stopped.
In rare cases, too many doses of colloidal silver can cause long-lasting severe health problems, such as kidney damage and seizures.
AgNPs exposure to human cells induces cytotoxicity, genotoxicity, and inflammatory response in human cells in a cell-type dependent manner. This has raised concerns regarding the use of AgNPs in therapeutics and drug delivery.
Scientific studies have documented a variety of adverse effects linked to prolonged exposure to silver nanoparticles, including bioaccumulation in internal organs such as the liver, spleen, kidneys, and brain, as well as oxidative stress, mitochondrial dysfunctions, DNA damage, and gene expression alterations. Of particular concern are the potential reproductive effects observed in animal models, with nanoparticles shown to cross the placental barrier and interfere with fetal development.
Colloidal silver products may interact with medicines, such as some antibiotics and levothyroxine (Unithroid, Levoxyl, and others). Colloidal silver may interfere with the body's absorption of the following drugs: penicillamine, quinolones, tetracyclines, and thyroxine.
Nanoparticulate silver-drug interactions may be mediated through induced oxidative stress in liver tissue, where the majority of systemically bioavailable silver nanoparticles is found. A prospective, single-blind, controlled in vivo human study investigated whether an orally ingested commercially available colloidal silver nanoproduct produces pharmacokinetic interference on select cytochrome P450 enzyme classes CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4.
According to the NCCIH, long-term and regular intake of colloidal silver may cause severe side effects such as argyria, systemic toxicity, interactions with antibiotics, and even poisoning. Claims that silver nanoparticles are naturally eliminated from the body after exerting their antimicrobial effect contradict findings related to bioaccumulation and tissue retention.
Silver in any form can have a toxic effect not only on pathogens but also on healthy cells. The biological activity and bioavailability of silver preparations depend on the degree of their solubility in water.
Silver has no known biological function in living organisms. There is accordingly no physiological basis for supplementation, and claims that "reduced silver levels in the body lead to reduced health" are unsupported by evidence.
Health conditions that Colloidal silver may help support.
Body systems that Colloidal silver may help support.
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