PUVA treatment inhibits nonimmunologic immediate contact reactions to benzoic acid and methyl nicotinate.

The effect of trioxsalen bath PUVA therapy on nonimmunologic immediate contact reactions (NIICRs) induced by benzoic acid (BA) and methyl nicotinate (MN) was studied in 12 dermatologic patients. One half of the back skin was covered with a cloth before each of ten irradiations on subsequent days. Four concentrations of each test substance were applied to the PUVA-exposed and nonexposed areas before any irradiation and after the 1st, 5th, and 10th PUVA treatment. Erythema and edema reactions were observed visually 40 minutes after BA and MN application, and changes in the skin blood flow were monitored using laser Doppler flowmetry (LDF). PUVA therapy suppressed the NIICRs in all concentrations of BA and MN on the PUVA-exposed area and occasionally on the nonexposed test sites. The suppressive effect was intesified during therapy.