Background
:
Skin sensitization with contact allergens is a result of both the intrinsic reactivity of the compounds and to what extent the compounds can penetrate the skin barrier.
Methods
:
The delivery of parabens (methyl, ethyl, propyl, butyl, and benzyl p-hydroxybenzoate) through full-thickness human skin in vitro decreased with increasing size of the alcohol moiety. Thus, the lower paraben homologue, methylparaben (MEP), permeated the skin about 10 times faster than butylparaben (BUP). During their diffusion through the skin the parabens are subjected to bioconversion according to the metabolizing capacity of the skin, as both the parent compound and p-hydroxybenzoic acid (PHBA) were found in the recipient phase.
Results
:
MEP was easily hydrolysed to PHBA acid and methanol in both full-thickness human skin homogenate and separate homogenates of epidermis and dermis. The hydrolysis followed Michaelis-Menten kinetics and was enzyme mediated, as no transformation was observed in homogenate deprived from enzymes by heat inactivation.
