Lip sun protection factor of a lipstick sunscreen

Objective: There is a well-documented need for effective human UVA and UVB photoprotection. Since there are important anatomical variations, the sun p rotection factor (SPF) of a lipstick sunscreen was measured on the anatomic al site intended for use. Methods: The SPF tests were performed according t o Federal US and European COLIPA guidelines. Prior to performing a test on the lip, the minimal erythemal dose (MED) of the unprotected back skin was determined. Subsequently, the sunscreen SPF was measured on the anatomical target site (lip). The evaluator was blinded with respect to scoring the SP F of each sunscreen treatment. Individual test sites were assigned to one o f the following treatment conditions: (1) no treatment (MED of unprotected skin); (2) test formulation; (3) reference standard. Results: The MED on un protected back skin was found to be 25% lower than on unprotected lip skin. The SPF of the lipstick sunscreen was measured 2 units lower than the SPF determined in the classical way on the back skin. Conclusion: It was hypoth esized that the higher MED of the lower lip compared with back skin was due to the adaptation of this tissue to the continuous exposure to UV radiatio n. Copyright (C) 2001 S. Karger AG, Basel.