Skin corrosivity potential of fatty acids: In vitro rat and human skin testing and QSAR studies

The corrosive potential of a series of fatty acids-propanoic acid (C3), butanoic acid (C4), hexanoic acid (C6), octanoic acid (C8), decanoic acid (C10) and dodecanoic acid (C12)-was investigated in the in vitro skin corrosivity test (IVSCT) using both rat skin and human skin. All the fatty acids with alkyl chain lengths up to and including C8 were found to be corrosive to rat skin. When human skin was used, the corrosive/non-corrosive threshold was shifted to around the C6 fatty acid. The results are discussed in the context of a QSAR for the corrosivity of organic acids, with the putative mechanism that corrosivity is a function of the ability of the chemical to permeate the skin together with its cytotoxicity, expressed in this case as acidity (pK(a)). This mechanistic interpretation is consistent with the known differences in barrier properties between rat and human skin.