Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease defined by recurrent nodules, tunnels (sinus tracts) and scarring involving the intertriginous
regions. The clinical course of HS is compatible with a biofilm-driven disease, and biofilm has been described in lesional HS skin. We therefore hypothesized
that clinically unaffected HS skin would also have an increased presence of biofilm compared with that of healthy controls. We conducted a case-control study, investigating the morphology of the axillary skin microbiota. Peptide nucleic acid – fluorescence in situ hybridization probes were used in combination with confocal laser scanning microscopy. Significant differences
were found in both distribution and quantity of the cutaneous microbiota in clinically non-affected axillary skin of patients with HS compared with healthy
controls. Surprisingly, we detected fewer bacteria and less biofilm in patients with HS. The reduced microbiota in patients with HS may play an important role in the early course of the disease.