Polymorphous light eruption: a common reaction uncommonly recognized.

Polymorphous light eruption (PMLE) is usually considered to be an uncommon complaint, although the prevalence in the general population has not been studied. In a survey of 271 apparently healthy subjects, 10% gave a history consistent with a diagnosis of PMLE. The clinical characteristics in the survey cases of PMLE were similar in most respects to those of patients presenting to a clinic with this disorder. However, there was one notable exception, in that there was a striking difference between the clinic and survey cases in the amount of sunlight required to trigger the eruption. Clinic patients required a mean exposure of 30 min as compared with over 3 h in the survey cases. These findings suggest that PMLE is a common disorder but that many individuals have a high threshold of response to sunlight exposure.