The mix of influences on skin conditions is demonstrated by hidradenitis suppurativa, an auto-immune disease with a genetic component in about a third of cases. Triggers can include an adverse reaction to the microbiome, or an abnormal microbiome whether on the skin surface or in the follicles, and secondary bacterial infections. Other triggers can be blocked follicles, abrasion (eg from clothing or skin folds), or cytokine release.25

It usually starts at puberty and can be most active in those aged 20 to 40, with the menopause often being an endpoint in women, suggesting sex hormones are a factor.25,26

Typical features are comedones, nodules and abscesses in hair follicles in apocrine sweat gland areas, such as axillae, groin and under the breast. The open wounds can be difficult to heal and can leave scarring. Many patients may also experience conditions such as acne, hirsutism or psoriasis and, less commonly, Crohn’s disease.