Pathogenesis of herpes simplex labialis: experimental induction of lesions with UV light.

To develop a model system of herpes simplex labialis which would enable the study of patients before lesion onset, five patients were exposed to various doses of UV light from a sunlamp at their usual site of lesions. Six of 10 treatments resulted in the development of herpes labialis. Three of four treatments with the highest exposure levels led to large, vesicular, virus culture-positive sores. Side effects from sunlamp exposure were minimal.