UV light from 290 to 325 nm, but not broad-band UVA or visible light, augments the formation of melanocytic nevi in a guinea-pig model for human nevi.

We have previously described a guinea-pig model where pigmented nevi similar to human nevi can be produced by application of low-dose topical 7,12-dimethylbenzanthracene (DMBA) followed by solar-simulated light. Five groups of guinea-pigs were used to test the effect of various spectral bands of solar-simulated light on low-dose DMBA-induced melanocytic nevi. Animals were irradiated with either UVB to near UVA2 (290-325 nm), UVA, visible light, full solar spectrum or no irradiation three times per wk for 12 mo to determine the broad-band effect of nevi-inducing irradiation.