Background: Cutaneous exposure to UVB radiation impairs the induction of contact hypersensitivity (CHS). Variable results have been found among studies examining the use of sunscreens to prevent UV-induced immunosuppression. Objective: Our purpose was to determine whether solar-simulated exposure of human skin resulted in an impairment of CHS responses and whether the preapplication of an intermediate sun protection factor (SPF) sunscreen could prevent this locally UV-induced immunosuppression. Methods: Irritant and CHS responses to dinitrochlorobenzene (DNCB) were randomly assessed in 160 human volunteers with or without UV exposure and with or without prior application of an SPF 15 sunscreen with high UVA protection. DNCB sensitization was performed 3 days after acute UV irradiation corresponding to 3 minimal erythema doses. Results: After solar-simulated UV exposure, the percentage of positive responses to DNCB sensitization dropped from 95% to 50% ( p = 0.003). Prior application of the sunscreen formulation did not modify the percentage of positive responses (90%) and maintained the immunization rate at 85% among volunteers exposed to UV. Conclusion: A localized sunburn can impair the afferent arm of CHS reactions in humans. The use of intermediate SPF sunscreens with high UVA protection adequately protects from the suppression of CHS responses that occurs after acute solar-simulated UV exposure.

(J Am Acad Dermatol 1997;37:187-94.)