Ozone, the main component of photochemical smog and air pollution, can damage 
the skin by oxidizing stratum corneum enzymes, lipids and structural proteins. 
We have developed a rapid screening assay to determine free radical scavenging 
capacity of various active ingredients that are frequently used in personal care 
products. Several known antioxidants including vitamin C, vitamin E analog 
Trolox, walnut seed extract, lipoic acid and ergothioneine inner salt were 
assayed for their ability to neutralize ozone-induced oxidation of 
beta-phycoerythrin, a fluorescent reporter protein derived from algae. The free 
radical scavenging capacities of these antioxidants were quantified and 
compared. The results demonstrate that this assay is a valuable primary 
screening tool for identifying antioxidant activity of natural or synthetic 
substrates that can be used in personal care products to protect the uppermost 
layer of our skin from oxidizing damage induced by O3.