 (See gut microbiota)

Psoriasis vulgaris typically affects drier skin sites such as elbows and knees.Dry areas of the skin tend to have high microbial diversity and fewer populations than sebaceous sites.A study using swab sampling techniques show areas rich in Firmicutes (mainly "Streptococcus" and "Staphylococcus") and Actinobacteria (mainly "Corynebacterium" and "Propionibacterium") are associated with psoriasis.