SUSCEPTIBILITY TO HERPES LABIALIS FOLLOWING MULTIPLE EXPERIMENTAL EXPOSURES TO ULTRAVIOLET-RADIATION

We studied susceptibility to herpes labialis by exposing 20 volunteers to experimental ultraviolet radiation (UVR) on three occasions at 3- to 4-month intervals. The number of patients who developed lesions aft er each session was 9/20 (45%), 9/20 (45%) and 14/20 (70%). Herpes sim plex virus (HSV) was isolated from 21/29 (72%) of lesions sampled. Thr ee patients never developed a lesion, 13 developed lesions on one or t wo of the three occasions, and 4 patients had a lesion following all t hree sessions. Seven of 33 (21%) lesions were 'immediate' lesions (dev eloped within 48 h) and the others developed 3-7 days after UVR exposu re (delayed lesions). Development of lesions correlated with historica l susceptibility to sun-induced herpes labialis, but not with age, sex , years with herpes labialis, frequency of herpes labialis from all ca uses, or concurrent serum levels of cortisol, dehydroepiandrosterone, estradiol, progesterone or alpha(1)-antitrypsin. Among normally menstr uating females, a significant association was identified between the d evelopment of herpes labialis and the luteal phase of the menstrual cy cle (8 cases of herpes labialis/11 attempts, RR = 14, P = 0.005). The lack of correlation between episodes of natural herpes labialis and su sceptibility to experimental UVR-induced disease suggests that these e vents are controlled differently. The results of serial attempts to in duce experimental herpes in each patient was most commonly inconsisten t, indicating that individual patient susceptibility to UVR varies ove r time. While the explanation for this variation remains unclear, stag es of the menstrual cycle may be important among women.