α-Lipoic acid as a topical antioxidant: Lin et al report that α-lipoic acid is ineffective as a topical antioxidant. This contradicts a previously published study that proposed α-lipoic acid as an antioxidant for topical application to protect the skin against ultraviolet photodamage including skin cancer and photoaging changes.
Lin’s study compared two commercial formulations. Formulation 1 contained 15% L-ascorbic acid (vitamin C) and 1% DL-α-tocopherol (vitamin E)a. Formulation 2 contained 5% α-lipoic acidb. These formulations were applied to the shaved back skin of Yorkshire pigs daily for four days and exposed to equal amounts of UV radiation, after which protection was evaluated by sunburn cell analysis and erythema reduction. When untreated skin was compared to skin treated with 5% α-lipoic acid, either alone or in Formulation 2, no significant protection could be detected. However, Formulation 1 (with no α-lipoic acid) did provide meaningful protection.