Enzyme that, when applied topically on skin, appears to be a very good antioxidant. Taken internally, alpha lipoic acid is a water- and fat-soluble antioxidant capable of regenerating other antioxidants, such as vitamins C and E. It is also believed to exert numerous soothing effects.
It’s clear from the research that alpha lipoic acid is a potent antioxidant, but it isn’t the only one; there are lots of great antioxidants for skin—in fact, there isn’t a lot of research on topical application of alpha lipoic acid.
Alpha lipoic acid is also known as thioctic acid; it’s extremely vulnerable to degradation by sunlight. Higher concentrations (5% or greater) are capable of causing a burning or stinging sensation on skin.
References for this information:
Acta Cirurgica Brasileira, October 2013, pages 708-715
Journal of Clinical Biochemistry and Nutrition, May 2009, issue 3, pages 218-222
The British Journal of Dermatology, October 2003, issue 4, pages 841-849
Clinical and Experimental Dermatology, October 2001, issue 7, pages 578-582