Metformin-induced allergic reactions
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Metformin-Induced Allergic Reactions: Incidence and Clinical Manifestations
Allergic reactions to metformin are rare but have been documented. The most common side effects of metformin are gastrointestinal, but hypersensitivity reactions can occur. These reactions may present as skin lesions, such as purpuric rashes, which typically resolve after discontinuing the drug. In a reported case, a patient developed purpuric skin lesions shortly after starting metformin, which subsided once the medication was stopped and replaced with an alternative therapy . Literature analysis of adverse drug reactions to metformin found that allergic reactions accounted for about 15% of reported cases, with skin and appendage lesions being a notable manifestation .
Metformin’s Effects on Allergic and Inflammatory Responses
Anti-Inflammatory and Anti-Allergic Properties
Several studies have shown that metformin may actually reduce allergic and inflammatory responses in experimental models. In mouse models of allergic asthma, metformin treatment significantly reduced airway inflammation, cytokine levels, and markers of airway remodeling. This effect is linked to the restoration of AMPKα activity and decreased asthma-related angiogenesis . Similarly, in obese mice with allergic eosinophilic inflammation, metformin reduced tissue eosinophil infiltration and normalized inflammatory markers, suggesting a protective role against asthma exacerbation .
Modulation of Mast Cell Activation
Metformin has been shown to suppress mast cell activation, which is central to allergic reactions. It inhibits both IgE- and aryl hydrocarbon receptor-mediated mast cell degranulation and cytokine release in vitro and in vivo. This suppression leads to reduced allergic responses, including passive cutaneous anaphylaxis, indicating that metformin may help control allergic diseases, especially in patients with comorbid diabetes .
Amelioration of Allergic Contact Dermatitis
In models of allergic contact dermatitis, metformin reduced the production of proinflammatory cytokines and nitric oxide, and improved autophagic flux in immune cells. These effects led to decreased inflammation and amelioration of dermatitis symptoms, suggesting a potential therapeutic benefit for allergic skin conditions .
Conclusion
While metformin-induced allergic reactions are rare, they can occur and may present as skin lesions. However, most research indicates that metformin generally has anti-inflammatory and anti-allergic effects, reducing symptoms in models of asthma, mast cell-mediated reactions, and allergic dermatitis 1256. Clinicians should remain vigilant for rare hypersensitivity reactions but can also consider the broader anti-allergic potential of metformin in certain patient populations 34.
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