Rashes

Skin reactions and nose reactions look different in the gut too

Rashes have many causes, from allergic reactions to irritation to underlying inflammatory skin conditions, several of which are covered in more detail elsewhere on this site. A pilot study comparing the gut bacteria of people with eczema, chronic hives, and allergic rhinitis found something genuinely interesting: bacteria from the Bacteroidales family showed up distinctly in both skin-based allergic conditions, eczema and hives, compared with allergic rhinitis, which affects the nose rather than the skin.

Source: Differences in gut microbiota between allergic rhinitis, atopic dermatitis, and skin urticaria: A pilot study

A specific bacterium linked to hives specifically

Within that pilot study, one particular species, Bacteroides plebeius, was significantly associated with the hives subgroup specifically, distinguishing it from both eczema and allergic rhinitis. This kind of specificity, different bacteria patterns for different manifestations of allergic reaction, supports the idea of a genuine gut-skin axis rather than allergic disease simply being one uniform process wherever it shows up in the body.

Broader research across several skin conditions agrees

A larger Mendelian randomization study looking at causal links between gut bacteria and six different inflammatory skin conditions, including psoriasis, rosacea, eczema, and acne, found 76 distinct causal relationships in total, with Lactobacilli and Bifidobacteria repeatedly identified as protective across multiple conditions. This adds broader support to the idea that gut bacteria composition genuinely shapes skin reaction patterns, not just in one specific rash-causing condition but across several.

Source: The causal relationship between gut microbiota and inflammatory dermatoses: a Mendelian randomization study

What this means for you

A new or unexplained rash, especially one that's spreading, painful, blistering, or accompanied by fever, needs medical assessment, since rashes have many possible causes that need their own specific diagnosis and treatment. If a rash turns out to be a manifestation of eczema, hives, psoriasis, rosacea, or acne, this site has a dedicated page on each with more specific evidence. In the meantime, a varied, plant-rich diet supports the same broad category of protective gut bacteria, including Lactobacilli and Bifidobacteria, that this research repeatedly ties to calmer inflammatory skin reactions. That's the same idea behind GutLab, everyday gut health starts with regularly feeding the microbiome a broad range of plant-rich ingredients.