Current issues of ACP Journal Club are published in Annals of Internal Medicine


Therapeutics

Sunscreen reduced recurrent herpes labialis caused by ultraviolet light

ACP J Club. 1992 May-June;116:82. doi:10.7326/ACPJC-1992-116-3-082


Source Citation

Rooney JF, Bryson Y, Mannix ML, et al. Prevention of ultraviolet-light-induced herpes labialis by sunscreen. Lancet. 1991 Dec 7;338:1419-22.


Abstract

Objective

To determine if sunscreen prevents reactivation of herpes labialis by ultraviolet B (UVB) light in predisposed individuals.

Design

Randomized, double-blind, placebo-controlled, crossover trial.

Setting

A clinical center at the National Institutes of Health and the University of California at Los Angeles Medical Center.

Patients

30 women and 8 men between 18 and 60 years of age, seropositive for herpes simplex virus (HSV), with a history of ≥ 1 recurrence per year of herpes labialis, who had not used an antiviral agent in the previous 30 days, and who did not have contact hypersensitivity to para-aminobenzoic, acid-based sunscreens were recruited. Mean age was 37 (SE 1.6) years, number of years with recurrent herpes infections was 26 (2.1), and reported frequency of recurrence was 2.7 (0.2) episodes per year.

Intervention

A minimum erythema dose was established for each participant. Exposure sites (left or right upper and lower lip) were chosen based on previous occurrences. Participants were exposed on 2 occasions, after application of sunscreen or placebo, to 4 times their previously determined minimum erythema dose by a fluorescent light source emitting mainly UVB light (290 nm to 320 nm). Exposures were ≥ 3 weeks apart. The commercially available sunscreen preparation had a sun protection factor (SPF) of 15. Participants were seen on the day of exposure, and 3 and 5 days later, or within 24 hours of onset of recurrence.

Main outcome measure

UV-induced recurrence, defined as a clinically or virologically confirmed HSV outbreak that developed ≤ 7 days after exposure and ≤ 1 cm from the exposure site.

Main results

38 placebo exposures and 35 sunscreen exposures were included in the analysis. Within 1 week of exposure, 27 placebo-treated participants developed recurrences (71%) compared with 1 participant (3%) who received sunscreen (P < 0.001). 25 of the 27 had positive viral cultures. With sunscreen there were no clinical lesions, but 1 person shed virus at the exposure site {This absolute risk reduction of 68% means that 2 patients would need to receive sunscreen (compared with placebo) to prevent 1 additional recurrence of herpes labialis, 95% CI 1 to 2; the relative risk reduction was 96%, CI 79% to 99%.}* All recurrences were at the site of exposure. No individual had a recurrence in the second or third week after exposure. The mean time to recurrence was 2.9 (SE 0.2) days. Investigators and participants, when asked 3 days after UVB exposure, correctly identified the placebo in > 80% of cases.

Conclusion

Compared with placebo, sunscreen (protection factor 15) reduces the rate of recurrent herpes labialis caused by ultraviolet light in predisposed individuals.

Source of funding: Eclipse Laboratories (placebo).

Address for article reprint: Dr. J.F. Rooney, Laboratory of Oral Medicine, National Institute of Dental Research, Building 30, Room 121, National Institutes of Health, Bethesda, MD 20892, USA.

*Numbers calculated from data in article.


Commentary

The finding that clinical lesions could be induced by an artificial light source on the lips of 71% of adult subjects with a previous history of labial herpes simplex is impressive, particularly because some study participants gave no history of sun exposure as a contributing factor. The amount of UVB radiation appears to be important in the authors' success because previous studies using natural sunlight did not achieve similar results. Four times the minimal erythema dose of UVB is a substantial dose, being equivalent to 80 minutes of midday midsummer sun exposure in a light-skinned person. Considering current media and professional reporting on the dangers of UV light exposure and the depletion of the ozone layer, I hope that fewer fair-skinned individuals will voluntarily expose themselves without protection to 80 minutes of midday midsummer sun.

Sunscreens do not prevent UV-induced changes in the skin, particularly in the skin's immune functions. As noted by Morison (1), sunscreen containing para-aminobenzoic acid gives only partial protection against UVB-induced suppression of chemically induced contact hypersensitivity and histologic changes in the skin. Morison also showed that mice protected with sunscreen were not significantly protected from growth of UVB-induced tumor. As suggested by the authors, protection from erythema may be the operative mechanism in preventing herpes labialis.

Based on this study, persons with a history of recurrent labial herpes simplex would be wise to routinely apply a sunscreen of SPF 15 or higher before any significant exposure to sunlight.

Don Rosenthal, MD
McMaster UniversityHamilton, Ontario, Canada


Reference

1. Morison WL. The effect of sunscreen containing para-aminobenzoic acid on the systemic immunologic alterations induced in mice by exposure to UVB radiation. J Invest Dermatol. 1984;83:405-7.