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UVA filters in
sunscreens enhance the protection against photoimmunosuppression
Fourtanier, Anny1,
Moyal, Dominique1, Baron, Elma2,
Compan, Delphine1 and Stevens, Seth2
L'Oréal Recherche, Paris, France1
University Hospitals Research Insitute / Case Western Reserve University,
Cleveland, OH2
Abstract-
Several studies have indicated that sunscreens failed to give comparable
protection against sunburn and photoimmunosuppression. One possible
reason for this discrepancy may be inadequate UVA protection. To answer
this question, we conducted studies in human volunteers in which we
compared the immunoprotective efficacy of sunscreens with different
UVA protection levels. We evaluated UV induced inhibition of either
the elicitation of delayed type hypersensitivity (DTH) response to recall
antigens after repeated low dose of exposures, or the induction of local
contact hypersensitivity (CHS) response to a chemical hapten (DNCB)
after acute UV exposure. Unprotected volunteer responses to DTH elicitation
tests were significantly reduced following repeated UVA, solar simulated
radiation (SSR), and real sun exposure conditions. Significant inhibition
of CHS induction was measured after an acute dose of only 0.5 minimal
erythema dose of SSR. In all experiments, the sunscreens reduced UV-induced
immunosuppression. The products with higher UVA protection factors (UVA-PF)
measured by the persistent pigment darkening method always showed significantly
greater protection. The acute UV exposure study allowed us to generate
dose-responses for inhibition of CHS with and without sunscreens and
to estimate immune protection factors (IPF). Using this protocol we
compared two broad-spectrum sunscreens with a same labeled sunburn protection
factor (SPF 15) but with different UVA-PF (respectively 10.5 and 2.5).
The product with the high UVA protection had an IPF exceeding its SPF
whereas for the other product IPF equal SPF. The above studies clearly
demonstrate the role of UVA in the photoimmunosuppression phenomenon
together with the need for photoprotection products effectively covering
the entire UV spectrum with a well-balanced UVB/UVA protection.
Keywords: sunscreen,
photoimmunosuppression, UVA protection, protection factor
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