Rashes and Hives (Urticaria): A Comprehensive Reference in the Context of Nutrition and Natural Health
1. Definition and Overview
Urticaria is an inflammatory skin disorder that may occur in isolation or associated with angioedema and/or anaphylaxis. Clinically, it is characterized by the presence of smooth, erythematous or blanching, itchy swelling called wheals or hives, which greatly vary in size and shape and last less than 24 hours before fading to leave normal skin. The name urticaria is derived from the common European stinging nettle Urtica dioica.
A weal (or wheal) is a superficial skin-colored or pale skin swelling, usually surrounded by erythema, that lasts anything from a few minutes to 24 hours. Urticaria can co-exist with angioedema, which is a deeper swelling within the skin or mucous membranes. Hives may burn or sting. The patches of rash may appear on different body parts, with variable duration from minutes to days, and typically do not leave any long-lasting skin change.
Urticaria is a common disorder, occurring in 15–25% of individuals at some point in life. Fewer than 5% of cases last for more than six weeks (a condition known as chronic urticaria). The condition frequently recurs.
2. Classification
Urticaria (hives) is a common disorder that may be associated with angioedema (swelling that occurs beneath the skin). It is generally classified as acute or chronic, and chronic urticaria is further classified as spontaneous or inducible.
- Acute urticaria: Acute spontaneous urticaria lasts fewer than 6 weeks.
- Chronic spontaneous urticaria (CSU): Chronic spontaneous urticaria is a self-limited, mast cell–mediated skin disorder marked by recurrent episodes of hives, angioedema, or both lasting 6 weeks or longer.
- Chronic inducible urticaria (CIndU): Clinicians classify the condition as chronic inducible urticaria when specific physical stimuli, such as pressure, temperature changes, or vibration, trigger symptoms.
- Physical urticaria: Physical urticaria may be induced by mechanical and applied pressure, exercise, or exposure to cold, heat, sun, water, or vibration.
- Dermatographic urticaria: Hives caused by stroking the skin (often linear in appearance) are due to a benign condition called dermatographic urticaria.
- Urticarial vasculitis: Individual hives that are painful, last more than 24 hours, or leave a bruise as they heal are more likely to be a more serious condition called urticarial vasculitis.
Lesions typically present as pruritic pink-to-red papules or plaques that resolve within 24 hours without residual discoloration. Nearly 40% of patients experience concurrent angioedema, most often involving the lips, eyelids, genitals, or extremities.
3. Body Systems Involved
3.1 The Skin and Dermal Vasculature
Urticaria is dermal edema resulting from vascular dilatation and leakage of fluid into the skin in response to molecules released from mast cells. The major preformed mediator histamine produces a prototypic, short-lived urticaria. However, the clinical spectrum and pattern of lesions indicate that other molecules, including prostaglandins, leukotrienes, cytokines, and chemokines, are produced at different times after mast cell activation.
3.2 The Immune System and Mast Cells
A brief overview of the essential pathophysiological element in CSU centers on the mast cell. From what is known at present, the release of histamine and other mediators — such as platelet activating factor (PAF) and cytokines — by activated mast cells leads to sensory nerve stimulation, vasodilation and plasma extravasation, as well as the recruitment of other immune cells to the urticaria site. Moreover, the signals for activating mast cells leading to hives are incomplete, poorly understood, and appear complicated, intricate, and heterogeneous.
Urticaria is associated with immune responses, particularly Type I hypersensitivity reactions, where immunoglobulin E (IgE) plays a crucial role in triggering inflammation, leading to vascular dilation, increased permeability, smooth muscle contraction, and enhanced glandular secretion. The development and manifestation of urticaria are deeply rooted in immunopathological processes, specifically the intricate interactions between cellular infiltration, immune reactions, coagulation cascades, and autoantibodies.
It is now well established that urticaria may result from the binding of IgG auto-antibodies to IgE and/or to the receptor for IgE molecules on mast cells, thus corresponding to a type II hypersensitivity reaction. These autoimmune urticarias represent up to 50% of patients with chronic urticaria.
Nonimmunological urticarias result from mast cell activation through membrane receptors involved in innate immunity (e.g., complement, Toll-like, cytokine/chemokine, opioid receptors) or by direct toxicity of xenobiotics (haptens, drugs).
The dermal mast cell and its mediators may play a central role in chronic idiopathic urticaria. Other inflammatory cells, including lymphocytes and polymorphonuclear cells, have also been implicated.
3.3 The Autoimmune System
Chronic urticaria is defined as the presence of urticaria (hives) for at least 6 weeks. If physical urticarias and urticarial vasculitis are excluded, the remainder can be divided into autoimmune chronic urticaria (45%) and idiopathic chronic urticaria (55%). The autoimmune subgroup is associated with IgG anti-IgE receptor alpha subunit in 35–40% of patients and IgG anti-IgE in an additional 5–10%.
3.4 The Gastrointestinal System and Gut-Skin Axis
Chronic underlying infection and mental and emotional stress can sometimes precede the onset of CSU, and once established can exacerbate the symptoms. There is early evidence of dysbiosis within the gastrointestinal tract in people with CSU and reduced levels of vitamin D are also evident.
Studies on CSU patients predominantly showed that the relative abundance of beneficial bacteria was decreased (Firmicutes and Bacteroidetes), while that of opportunistic bacteria was increased (Enterobacteria and Proteobacteria). The intestinal microbiome of patients with chronic spontaneous urticaria is marked by reduced diversity, reduced relative abundance of butyrate-producing intestinal bacteria, and elevated levels of conditional pathogens.
3.5 The Thyroid and Endocrine System
Numerous autoimmune diseases such as systemic lupus erythematosus, polymyositis, dermatomyositis, and rheumatoid arthritis have been associated with chronic urticaria; however, autoimmune thyroid disease deserves special mention. A higher prevalence of antithyroid antibodies has been found, regardless of thyroid function (euthyroidism, hypo- and hyperthyroidism), in patients with chronic spontaneous urticaria.
3.6 The Neuroendocrine System
Stress is associated with the onset of the disease through the activation of the sympathetic and adrenomedullary system and the hypothalamic-pituitary-adrenal axis. Stress can increase the severity of itching of the skin and can cause the skin to be susceptible to eczema, psoriasis, acne, hives, and other types of rash.
4. Contributing and Associated Factors
4.1 Allergens and IgE-Mediated Triggers
Hives frequently occur following an infection or as a result of an allergic reaction such as to medication, insect bites, or food. For both acute and chronic urticaria, patients frequently report food as a precipitating cause. For acute urticaria, the foods that are associated with true allergies, such as nuts and shellfish, are the most frequent offenders.
4.2 Drugs and Chemical Compounds
Identified causes include drugs, foods, infections, immune complex production leading to urticarial vasculitis, autoimmune antibody production, and underlying autoimmune disease, particularly autoimmune thyroiditis. Drugs that have caused allergic reactions evidenced as hives include codeine, morphine sulfate, dextroamphetamine, aspirin, ibuprofen, and penicillin, among others.
4.3 Physical Triggers
Psychological stress, cold temperature, or vibration may also be a trigger. Urticarial lesions are generally thought to be the result of mast cell activation and degranulation, which is supported by the finding of increased levels of serum histamine during some urticarial flares.
4.4 Infection
Several infections have been linked to chronic urticaria. The best evidence is for Helicobacter pylori infection.
4.5 Autoimmune Thyroid Disease
A significant association between chronic urticaria and thyroid autoimmunity has been demonstrated, and tests to detect thyroid auto-antibodies are considered relevant in patients with chronic urticaria. The prevalence of chronic urticaria and anti-TPO antibody is notably high and may be related to sex hormones; therefore, in young women with chronic urticaria, especially in refractory cases, monitoring for anti-TPO is recommended. Anti-TPO and TSH should be evaluated for the diagnosis and treatment of patients with urticaria or chronic angioedema.
4.6 Pseudoallergens and Food-Related Non-IgE Reactions
In a subset of patients, pseudoallergens may induce or worsen chronic urticaria. Pseudoallergens include preservatives, dyes, salicylates, and aromatic compounds found in both natural (e.g., garlic, artichoke, tomatoes, fruits, and rhubarb) and processed foods (e.g., artificial sweeteners and processed meats). Unlike true allergens, skin prick testing is negative and exposure does not consistently result in clinical symptoms.
Foods might be responsible for urticaria if they are rich in histamine or are able to activate mast cells via the non-immunological pathway and induce histamine release. Foods that might be involved include cheese, fish, vegetables, fruits, chocolate, and alcohol. Contrary to acute urticaria being linked to food allergy, the mechanism in chronic spontaneous urticaria is not an IgE-mediated type I reaction, but is rather dose-dependent, usually a delayed pseudoallergic reaction to food coloring, artificial flavoring, or preservatives. Non-artificial natural ingredients in food might also cause pseudoallergic reactions.
4.7 Histamine Intolerance
When patients with histamine intolerance (HIT) develop urticaria-like rashes, HIT should be differentiated from other types of urticaria, such as spontaneous urticaria and artificial urticaria. Patients with HIT often have a history of eating foods that are rich in histamine. In laboratory examination, diamine oxidase (DAO) concentration is decreased in HIT. Common histamine-rich foods include mackerel, preserved meats, fermented cabbage, citrus fruit, and peanuts, as well as red wine and matured cheese.
4.8 Gut Microbiome Dysbiosis
Growing evidence recognizes gut microbiota disturbance as a potential pathogenesis and aggravating factor of urticaria. Studies supporting this view have pointed out that patients with urticaria exhibit a distinct gut microbiota characterized by a reduction in beneficial intestinal bacteria and an increase in opportunistic pathogens compared to healthy individuals. This microbial imbalance may exacerbate eosinophil-driven skin inflammation through impaired intestinal barrier function and abnormal Th2/Th17 immune responses.
5. Nutrients, Herbs, and Natural Ingredients
5.1 Vitamin D
Scientific Evidence
A meta-analysis of seventeen studies comparing urticaria groups with controls revealed a mean difference of −9.35 ng/mL (95% CI −12.27 to −6.44) in serum 25(OH)D levels, and there was also an association of urticaria with vitamin D deficiency. Fourteen studies (1,321 CSU cases and 6,100 controls) were concerned with serum vitamin D levels in CSU patients. Twelve studies showed statistically significant lower serum vitamin D levels in CSU patients than the controls.
In subgroup analyses, significant effects of 25(OH)D were found among adult and chronic urticarial populations. Six vitamin D supplementation trials showed a significant reduction in clinical urticarial score on intervention with vitamin D.
Patients with chronic idiopathic urticaria significantly showed lower levels of vitamin D. Vitamin D deficiency was significantly associated with increased susceptibility to chronic idiopathic urticaria. There was a significant positive correlation between vitamin D levels and urticaria activity score.
One randomized trial conducted on 77 patients with CSU and 67 healthy controls randomized CSU patients to either 0.25 µg alfacalcidol daily or placebo for 12 weeks. Serum 25(OH)D was significantly lower in CSU patients as compared to healthy controls and was negatively correlated to urticarial severity. The investigators concluded that vitamin D deficiency is more common in CSU patients as compared to healthy people and that alfacalcidol might have a beneficial role as add-on therapy in CSU management.
In allergic conditions such as asthma, atopic dermatitis, and allergic rhinitis, vitamin D deficiency has been associated with heightened disease activity, increased exacerbation rates, and reduced responsiveness to conventional therapies. Similarly, in chronic urticaria, vitamin D may modulate mast cell stability, reduce histamine release, and attenuate inflammatory cytokine production, contributing to symptom relief.
Evidence strength: While some evidence suggests an association of chronic urticaria with vitamin D levels, measurement of vitamin D or supplementation is not currently a part of standard diagnostic or treatment recommendations. The association data are consistent across multiple studies, but supplementation trials remain heterogeneous in design, dose, and outcome measures.
5.2 Quercetin
Scientific Evidence
Quercetin is a polyphenolic compound found in fruits, vegetables, nuts, seeds, herbs, spices, and red wine with antioxidant properties. Flavonoids including quercetin have potent anti-oxidant, anti-inflammatory, and mast cell blocking activities. Several flavonoids can inhibit histamine release from murine mast cells, as well as IL-6 and TNF release from bone marrow-derived cultured murine mast cells and rat peritoneal mast cells.
In vitro experiments with human cord blood-derived mast cells (hCBMCs) demonstrated that preincubation with quercetin (100 µM) significantly reduced histamine secretion from 4,347.9 to 977.3 pg/mL (82% inhibition), prostaglandin D2 release from 3,771.8 to 882.5 pg/mL (77% inhibition), and leukotriene secretion from 4,628.6 to 35.3 pg/mL (99% inhibition), comparing favorably to the pharmaceutical mast cell stabilizer cromolyn.
Chronic urticaria is a skin allergy caused by the excessive activation of mast cells. One study mainly explored the therapeutic effect of quercetin in ovalbumin-induced CU mice and investigated its target and mechanism in vitro. The study results suggest that quercetin alleviates CU by activating the CD300f/SHP-1 signaling pathway.
Quercetin can selectively bind to CLM-1 on mast cells, leading to SHP-1 phosphorylation and subsequent inhibition of downstream MyD88/IKK/NF-κB signaling. Furthermore, activation of CLM-1 modulated the surface expression of MRGPRX2 by inhibiting F-actin. Quercetin is thus described as a promising treatment for allergic diseases by acting as a CLM-1 agonist that inhibits MRGPRX2-mediated mast cell degranulation.
Quercetin stabilizes mast cells, inhibits Lyn/PLCγ pathways, and improves rhinitis symptoms in small randomized trials using bioavailable formulations.
Evidence strength: Quercetin has been suggested for the treatment of urticaria symptoms due to its anti-inflammatory and antihistamine properties. Observational animal and small-scale human clinical studies have supported these claims. However, more extensive double-blind, placebo-controlled trials are necessary to confirm these results. The mechanistic evidence from cell and animal studies is robust, but large-scale clinical trials in urticaria specifically are lacking.
5.3 Omega-3 Polyunsaturated Fatty Acids
Scientific Evidence
Findings suggest that EPA and DHA as omega-3 fatty acids may have beneficial effects in modulating mast cell function and reducing inflammation, whereas omega-6 fatty acids such as arachidonic acid may have pro-inflammatory effects.
Omega-3 fatty acids modulate Th2 responses, promote regulatory T cells, and generate specialized pro-resolving mediators, with modest clinical benefits observed in pregnancy and early life.
The literature suggests that diets free from pseudoallergens and histamine-releasing foods may attenuate urticaria. Supplements such as fats (including omega-3 fatty acids), vitamin D, iron, and flavonoids have also been studied and may diminish symptoms.
Evidence strength: Most evidence for omega-3 fatty acids in urticaria specifically comes from cell-based studies and mechanistic data rather than dedicated urticaria clinical trials. The evidence is preliminary and indirect, drawn from broader immunomodulatory research in allergic conditions.
5.4 Probiotics and Gut Microbiome Modulation
Scientific Evidence
Clinical trials have demonstrated that specific strains of lactic acid bacteria, such as L. gasseri, L. salivarius, L. johnsonii, L. paracasei, and L. reuteri, either individually or in combination with Bifidobacteria strains (e.g., B. animalis and B. longum), can reduce urticaria severity and improve patients' quality of life.
One clinical trial compared the effects of loratadine combined with probiotics versus loratadine alone in the treatment of chronic urticaria. The results showed that loratadine combined with a multi-strain probiotic preparation comprising Bifidobacterium infantis, Lactobacillus acidophilus, Enterococcus faecalis, and Bacillus cereus significantly reduced pruritus and wheal formation, and increased serum levels of interferon-gamma (IFN-γ), compared to loratadine without probiotics.
A four-way blind randomized clinical trial conducted on patients with chronic urticaria who did not respond well to first-line antihistamine treatment administered antihistamine (cetirizine) and probiotics (femilact capsule) to the intervention group, and antihistamine and placebo to the control group, twice daily for 8 weeks. The Urticaria Activity for 7 Days (UAS7) questionnaire was used to assess urticaria activity. Mean UAS7 scores were reduced in both groups but were more significant in the probiotic intervention group (9.6 ± 6.4) compared to the control group (12.7 ± 8.1) at the end of week eight (P = 0.036). However, there was no significant difference in quality of life between the two groups. This study showed that probiotic consumption along with antihistamines significantly improved urticaria activity but not quality of life.
A recent study showed that, when compared with ebastine (a second-generation H1-antihistamine), the combination of Lactobacillus reuteri and ebastine can significantly alleviate clinical symptoms and enhance quality-of-life scores in patients with chronic urticaria. A meta-analysis suggested that probiotics combined with antihistamines may enhance therapeutic efficacy in urticaria treatment. However, this meta-analysis included studies on other allergic skin conditions such as eczema and atopic dermatitis, introducing considerable clinical heterogeneity. Moreover, it lacked a clear definition of "therapeutic effect" and did not report internationally recognized outcome measures, raising concerns about reliability and generalizability.
One clinical trial reported that probiotics reduced serum IL-6, TNF-α, and IgE as well as peripheral blood CD8+ levels in patients with chronic spontaneous urticaria.
Evidence strength: A limitation across studies is small sample size, variable diagnostic criteria for CSU, and short follow-up duration. A 2023 systematic review and meta-analysis of nine small clinical trials concluded that while probiotic supplementation may offer modest symptom relief, the overall quality of evidence remains low, and larger, well-designed RCTs are needed to establish clinical efficacy.
5.5 Stinging Nettle (Urtica dioica)
Traditional Use
Stinging nettles (Urtica spp.) have been used in a diverse range of traditional and historical medicines from around the world for the treatment of skin diseases, wounds, urinary disorders, respiratory diseases, bone and joint pain, anaemia and other circulatory problems, as well as in cosmetic preparations for skin and haircare. Several bioactive chemical components from stinging nettle have been identified, including flavonoids, phenolic and amino acids, fatty acids, and carotenoids.
Scientific Evidence
Stinging nettle has been suggested for its anti-inflammatory and antihistamine properties. However, the evidence remains largely preliminary. It should be noted that physical contact with stinging nettles (Urtica dioica) most commonly itself causes an urticarial skin reaction — a distinction that is important when considering the oral use of nettle preparations versus topical contact.
Evidence strength: Clinical evidence directly supporting stinging nettle in the management of urticaria is limited. Traditional use is well-documented across multiple cultures, but rigorous clinical trials in urticaria are absent from the current literature.
5.6 Dietary Flavonoids Broadly (Including Curcumin and EGCG)
Scientific Evidence
Curcumin inhibits NF-κB/MAPK signaling, enhances barrier function, and improves allergic rhinitis and dermatitis, despite limited bioavailability. Epigallocatechin gallate (EGCG) stabilizes mast cells, attenuates FcεRI signaling, and reduces airway inflammation in preclinical models, though clinical data are scarce.
Overall, preclinical findings consistently support the immunomodulatory potential of these compounds, while clinical results are promising but heterogeneous. Standardized formulations, long-term trials, and exploration of synergistic effects are required to confirm efficacy and safety.
Evidence strength: Evidence for curcumin and EGCG in urticaria specifically is preliminary and primarily preclinical (animal and cell studies). No large clinical trials in urticaria populations have been published.
5.7 Short-Chain Fatty Acids (SCFAs) and Butyrate
Scientific Evidence
The SCFA butyrate suppressed IgE-mediated bone marrow-derived mast cell release of TNF-α and IL-6 (approximately 70%) in a FcεRI-dependent manner. Phosphorylation of MAPK p38, ERK1/2, and c-Jun N-terminal kinase (JNK) was downregulated by butyrate. Additionally, butyrate treatment increased acetylation in the promoters of TNF-α and IL-6, but blocked the binding of RNA polymerase II to these genes, resulting in suppressed transcription initiation.
The intestinal microbiome of patients with chronic spontaneous urticaria is marked by reduced diversity and reduced relative abundance of butyrate-producing intestinal bacteria. The connection between butyrate-producing bacteria, SCFA production, and urticaria disease activity is an emerging area, though evidence remains preclinical.
Evidence strength: Mechanistic cell-based evidence only; no clinical trials in urticaria populations have evaluated dietary butyrate or SCFA-boosting strategies specifically.
6. Dietary Factors
6.1 Pseudoallergen-Free (PAF) Diet
Patients with chronic urticaria (CU) often ask about dietary modification. Research has indicated that specific dietary changes may be helpful in a subset of patients. Immunological food reactions are rare, but potential triggers of CU include those seen in certain settings, as in patients with a history of tick bites, a history of raw or marinated fish ingestion, or those with celiac disease. Nonimmunological food intolerances may also contribute, although the mechanism of action is not well understood.
Strategies for diets in chronic spontaneous urticaria (CSU) are controversial. A systematic review assessed the interest in diet for managing CSU, searching MEDLINE, EMBASE, CENTRAL, and LILACS. Among 278 reports screened, 20 were included, involving 1,734 patients. Reports described 3 types of systematic diet: pseudoallergen-free diet (n = 1,555 patients), low-histamine diet (n = 223) and diet without fish products (n = 47), which induced complete remission in 4.8%, 11.7%, and 10.6% of patients, respectively, and partial remission in 37.0%, 43.9%, and 4.3%.
Eight reports described personalized exclusion diets (66 patients) adapted to symptoms/allergological test results and led to complete remission in 74.6% of patients, although the diagnosis of CSU was doubtful. No comparative randomized studies of diets were available.
6.2 Low-Histamine Diet
Trials of pseudoallergen-free diets and low-histamine diets have resulted in partial remission in a subset of patients, while oral provocation testing has confirmed that some patients experience worsening of symptoms after ingestion of food additives, tomatoes, herbs, seafood, alcohol, and other foods.
The relationship between diet and chronic urticaria is not as firmly defined as in acute urticaria. Many patients unnecessarily restrict their diets, so it becomes the role of clinicians to help patients identify if there is a reproducible link between their symptoms and their dietary exposures.
6.3 Vitamin D and Nutritional Status
An increased prevalence of vitamin D deficiency has been noted in patients with CU compared with healthy controls. There is early evidence of dysbiosis within the gastrointestinal tract in people with CSU, and reduced levels of vitamin D are also evident. The latter may be related to the importance of vitamin D3 in increasing T regulatory function, which can control a tendency to autoimmunity.
7. Lifestyle Factors
7.1 Psychological Stress
Chronic underlying infection and mental and emotional stress can sometimes precede the onset of CSU, and once established can exacerbate the symptoms. Stress is associated with the onset of the disease through the activation of the sympathetic and adrenomedullary system and the hypothalamic-pituitary-adrenal axis. Talking therapies that reduce stress and anxiety, vitamin D3 supplementation, correction of intestinal dysbiosis, and treatment of any chronic infection should be considered as part of an integrative approach to the management of recalcitrant CSU.
7.2 Physical Triggers and Environmental Exposures
Chronic urticaria causes recurrent episodes of pruritic wheals, angioedema, or both lasting 6 weeks or longer. The condition is classified as CSU when symptoms occur without an identifiable trigger, and as CIndU when symptoms result from specific physical stimuli, such as pressure, temperature extremes, or vibration.
7.3 Symptomatic Lifestyle Measures
Applying cold compresses, wearing loose-fitting clothing, and soaking in oatmeal baths are lifestyle choices that may help relieve the symptoms of urticaria. These measures are widely described but are supportive and symptomatic rather than mechanistically curative.
7.4 The Gut–Skin Axis and Microbiome
By applying new knowledge on gut microbial communities and metabolomics, future CSU therapies could modify the microbiota composition using agents such as probiotics or other similar agents, which, in combination with current standard therapies, could hopefully lead to a reduction in symptoms and an improved quality of life. Therapeutic strategies targeting the gut-skin axis offer novel avenues for innovative dermatological treatments, with future breakthroughs potentially involving microbial community engineering, postbiotics, and artificial intelligence in microbiome-related diagnostics.
8. Summary of Evidence Strength by Factor
- Vitamin D deficiency association: Consistent across multiple observational studies and meta-analyses; supplementation trials show signal of benefit but remain heterogeneous. Evidence level: moderate.
- Pseudoallergen-free and low-histamine diets: Systematic reviews show partial remission in subsets of patients; no randomized comparative diet trials available. Evidence level: low-to-moderate for certain subpopulations.
- Quercetin: Robust mechanistic evidence from cell and animal studies; small-scale human studies in allergic conditions; no large RCTs in urticaria specifically. Evidence level: preliminary.
- Probiotics: Multiple small RCTs show modest benefit when combined with antihistamines; overall evidence quality is low due to small sample sizes, heterogeneity, and lack of standardization. Evidence level: low-to-moderate.
- Omega-3 fatty acids: Cell-based mechanistic data; modest clinical evidence in broader allergic disease. No dedicated urticaria clinical trials. Evidence level: preliminary.
- Stinging nettle (Urtica dioica): Traditional use well documented; no rigorous clinical trials in urticaria. Evidence level: insufficient/traditional only.
- Curcumin, EGCG, and other flavonoids: Preclinical mechanistic evidence; no large clinical trials in urticaria. Evidence level: preliminary/preclinical.
- Gut microbiome/butyrate: Early associative evidence linking dysbiosis to CSU; SCFA data are cell-based only. Evidence level: emerging/preclinical.
References
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