Side effects of laser therapy, modified by ultraviolet irradiation and para-aminobenzoic acid in mice.

Scarring is a well-known side-effect of cutaneous laser treatment and exposure to solar ultraviolet radiation is suspected to increase scar formation. We investigated how wounds and scarring were modified by interfering in the laser-induced inflammation using ultraviolet radiation and para-aminobenzoic acid. A copper vapour laser operating at 578 nm was used at three different intensities and doses. The ultraviolet radiation was administered three times weekly prior to and four times weekly after the laser treatment. The daily dose was 21.5 kJ/m2 equivalent to 3.5 Basic-MED. The laser-induced wounds were evaluated daily and histological and biochemical analyses were used to estimate scarring. Ultraviolet irradiation resulted at some of the used laser intensities in decreased scores of maximum wound area, wound healing time, cumulated wound area, and a decreased skin content of hydroxyproline, whereas the degree of the chronic fibrosis tended to increase. Application of para-aminobenzoic acid before the solar ultraviolet irradiation did not change the acute wound scores but reduced, although not significantly, the degree of fibrosis.