Photochemotherapy of psoriasis: effects on bacteria and surface lipids in uninvolved skin

The effect of PUVA therapy for psoriasis on the microbial flora and on levels and composition of skin surface lipid has been studied in ten patients. Samples were obtained from clinically uninvolved skin from the back and the forearm. There was no consistent significant change in the viable counts of aerobic cocci or anaerobic coryneforms during therapy. A transient rise in Staphylococcus aureus counts was thought to be due to the use of emollients rather than to an effect of PUVA. Genetic changes in the microorganisms were not sought. There was an increase in the amount of total lipid (both casual levels and replacement sums) during therapy. An increase of free fatty acids at the expense of triglycerides did not reach statistical significance. The influence of PUVA on the skin flora seems to be less in vivo than anticipated from in vitro studies.