A Comparison Study of Nonanoic Acid and Sodium Lauryl Sulfate in Skin Irritation

The cutaneous response to irritants can be influenced by various factors including the characteristic of irritants, the mode of exposure, environmental and host-related factors. It has been suggested that irritants can be divided into two types: corrosive and noncorrosive. Sodium lauryl sulfate (SLS) has been considered as a typical corrosive irritant and nonanoic acid (NAA) an example of a noncorrosive irritant. We applied SLS and NAA solutions on the volar forearm skin for 24 h and measured transepidermal water loss (TEWL) and erythema indices to evaluate some differences in the profile of irritant reaction and skin functions between corrosive and noncorrosive irritation. In our study of TEWL measurements, SLS solutions caused higher TEWL values than NAA solutions, and the slope of the SLS curve was steeper than that of the NAA curve in relation to the concentrations of SLS and NAA. There was a tendency for the TEWL values to plateau at higher NAA concentrations. In the study of the time course of TEWL and erythema indices, TEWL values returned to baseline after 3 weeks in areas patch-tested with 50% NAA, but they did not recover baseline values until 3 weeks in the corresponding areas tested with 5% SLS. However, both SLS and NAA solutions showed a very similar pattern of erythema indices. Our data suggest that skin injuries induced by SLS might need a more prolonged recovery time for TEWL than NAA injuries. SLS, the corrosive irritant, showed a different pattern of cutaneous functional change compared with NAA, the noncorrosive irritant. NAA could also be considered as one of the model irritants in a study of irritant contact dermatitis using a noncorrosive irritant.