Effects of infra-red and neodymium yttrium aluminium garnet laser irradiation on non-immunologic immediate contact reactions to benzoic acid and methyl nicotinate.

Effects of infra-red A (IRA) (600-2000 nm) and 1064 nm laser irradiation on non-immunologic immediate contact reactions (NIICRs) induced by benzoic acid (BA) and methyl nicotinate (MN) were studied. Five concentrations of BA and MN in petrolatum were tested, on two subsequent days, without occlusion on the upper arm of 10 or 12 test subjects, with a dose of IRA irradiation that elevated surface temperature of the skin to 39.5 degrees C. In the first group exposed to IRA irradiation, the NIICR tests were performed immediately after the surface temperature of the skin had reached 39.5 degrees C; the skin was then allowed to cool down. In the second group exposed to IRA irradiation, the NIICRs were performed after a skin temperature of 39.5 degrees C was attained, and the skin temperature was kept unchanged for another 15 min. In the 1064 nm laser exposure group of 12 subjects, the tests were performed on the upper back immediately after irradiation of the skin with 100, 50, and 25 J/cm2 of neodymium yttrium aluminium garnet (Nd-YAG) laser (1064 nm). Reactions were monitored with laser-Doppler flowmetry 20 and 40 min after application, and erythema and edema reactions were graded visually. In the first group exposed to IRA, the warming had an enhancing effect on only one reaction induced by MN. In the second group exposed to IRA irradiation, the NIICRs occurring from BA on the exposure day were stronger on the exposed than both the reactions on the non-exposed area as well as the responses to MN on the irradiated area on the following day only.(ABSTRACT TRUNCATED AT 250 WORDS)