Pigmentary changes after pulsed dye laser treatment in 125 northern European patients with port wine stains.

We investigated the occurrence of pigmentary changes after flash lamp pumped dye laser treatment in 125 Norwegian patients. Post-treatment hyperpigmentation occurred with equal frequency during summer and winter (23%), and the facial regions did not exhibit higher occurrence than lesions located elsewhere. The patients that achieved hyperpigmented skin were not exposed to any higher fluence than those without this complication. On the contrary, we found that during the summer period from April to September the patients with post-treatment hyperpigmentation had been exposed to a significantly lower dose than those without pigmentary changes. These results indicate that the epidermal melanin content is not the only criterion for obtaining post-treatment hyperpigmentation. There might also be a constitutional disposition. In predisposed individuals the threshold dose for hyperpigmentation might be reduced in summer when the skin is more pigmented.