Comparision of Results of Sting Tests Using Various Kinds of Alpha Hydroxy Acids on Sensitive Skin

Background: Users of cosmetics and skin care products often report adverse reactions ranging from itching, stinging and dryness to intense inflammatory responses such as erythema, wheals and rashes. Sensitive skin has been described as a skin type showing higher reactivity than normal skin, and it develops exaggerated reactions when exposed to internal stimulants and external irritants. The alpha hydroxy acids (AHAs), naturally occurring organic acids which include lactic acid, glycolic acid, citric acid, malic acid and tartaric acid are all kinds of noncorrosive irritants. The lactic acid sting test is widely accepted as a marker of sensitive skin and is employed for the selection of subjects experiencing invisible sensory irritation. Objective: This study was performed to compare the results of sting tests conducted on the sensitive and nonsensitive skin group which had been exposed to various kinds of AHAs. Methods: A total of 50 individuals (25 individuals with a sensitive skin group and 25 individuals with a nonsensitive skin group) were selected by the method of self-assessment questionnaires relating to sensitive skin. The subjects were tested on the face with 2 variables of 5 AHA types (with or without Hilltop chamber occlusion), at 2 weeks intervals, for a total of 10 times. Results: The positive response rate of stinging in the sensitive skin group was higher than that in the nonsensitive skin group for all tests except the glycolic acid sting test using Hilltop chamber (p