Assessment of the effect of a sunblock stick in the prevention of solar-simulating ultraviolet light-induced herpes labialis

Abstract

Sunlight exposure is one of the main factors triggering the recurrence of herpes labialis. We decided to test the hypothesis that recurrence could be prevented by the use of a high-protection sunblock stick. The preventive effect of a sunblock stick containing Mexoryl SX, Eusolex 6300 and Parsol 1789 was assessed in ultraviolet light-induced herpes labialis in comparison with its vehicle. A group of 19 consenting healthy volunteers (11 females and 8 males), with a history of at least two herpes labialis recurrences per year, aged from 19 to 48 years (mean age 32±10 years) were selected to participate in this randomized crossover study. The minimal erythema dose (MED) of each subject was first determined on the forearms. During a first phase, the sunblock or the vehicle stick was applied to the lips which were irradiated 10 min later with four times the MED. Clinical signs of herpes were evaluated after 3 and 5 days. A second phase was performed 4 weeks later with the product allocation reversed. Out of the 19 tested subjects, 11 had a herpes recurrence with the vehicle stick, and of these 11 subjects, only one had a herpes recurrence with the sunblock stick. These results show that the sunblock stick was significantly more effective (binomial test, P < 0.01) than its vehicle.

Key Words:

• Herpes labialis
• Sunscreen
• Ultraviolet light
• Mexoryl SX