Ascorbic acid contributes to the thickening and improvement of the epidermal barrier in an in vitro skin model, and to the reduction of cellular damage caused by oxidative stress in human dermal fibroblasts, so the aim of the study was to analyse skin pre-treatment with the antioxidant prior to PPD exposure.
The research, carried out by Procter & Gamble in Belgium and Germany, along with the University of Groningen and Trier University, investigated whether this pre-treatment reduces the elicitation of a contact allergic reaction in people allergic to the hair dye component, PPD.
Published in the journal Contact Dermatitis, the study chose a group of 12 subjects who were well characterised with respect to their contact allergic reaction to PPD (through history and patch tests) and to PPD-containing hair dye in a hair-dyeing simulation model.
Skin areas on the forearms were, in a left versus right design, exposed to an emulsion with ascorbic acid and an emulsion without ascorbic acid, and then to a 2% PPD-containing hair dye testing formulation.
In addition, control areas were exposed to the emulsions and to the PPD-containing hair dye formulation without pre-treatment. Skin reactions were graded on the second and third days.
The results showed that pre-treatment with ascorbic acid emulsion resulted in a reduction in the elicitation reaction in 7 of 12 subjects on the third day, and that no statistically significant difference was observed on the second day.
The researchers say that the main finding of this study was the reduced elicitation reaction to a PPD-containing hair dye when the skin was pre-treated with the antioxidant ascorbic acid as compared to without.
“In conclusion, the results of this, albeit small, study are indicative of a reduction in the allergic response of the skin upon pre-treatment with the antioxidant ascorbic acid,” they say.
The researchers do note that because the number of individuals included in this study is low, and the effect of the antioxidant is not large, a similar study with a more expanded reading protocol should be carried out.