The bacteriology of skin cysts *

Thirty‐nine clinically uninflamed cysts of the three most common varieties, epidermoid cysts, tri‐chilemmal cysts and steatocystoma multiplex were removed under sterile conditions and the contents cultured under aerobic and anaerobic conditions. Seventy‐three percent of epidermoid cysts grew significant numbers of organisms whereas none of the trichilemmal cysts did so. The organisms found were the common skin commensals, Staphylococcus epidermidis biotype I, anaerobic Gram positive cocci of the Gaffya type and Corynebacterium acnes Type I. This indicates that cysts which clinically have a punctum, namely epidermoid cysts, may become colonized with surface bacteria under normal circumstances. If they become colonized with pathogenic bacteria they become inflamed, a not uncommon clinical picture. The results from patients with steatocystoma multiplex were difficult to interpret because of the small numbers of patients involved and the unusual clinical appearance they presented.