Fate of ethanol topically applied to skin

Ethanol is a major component of many aerosol sprays and consumer products that are designed to contact the skin. It is theoretically possible that small amounts of ethanol from alcohol-based sprays can be absorbed across the skin or inhaled during spraying. In order to assess the potential systemic dose, three parameters were measured: the evaporation of [14C]ethanol from the skin surface, the in vitro penetration of [14C]ethanol through excised pig skin and the ethanol concentration in the blood of human volunteers following simulated use of an alcohol based deodorant spray. The rate of evaporation from Benchkote® and whole pig skin was similar (t1/2=13.6 sec and 11.7 sec, respectively) while that from glass was longer (t1/2=24.8 sec). Ethanol penetration through pig skin in vitro was greater in occluded cells than in non-occluded cells (2.19 mg/cm2 and 0.10 mg/cm2 in 24 hours, respectively). At the maximum flux seen in this experiment under occlusion, the amount of ethanol penetrating from a 1 m2 area of skin would give a blood alcohol level of about 4 mg% in a 70-kg man. In the human use study, none of the blood samples taken from 16 human volunteers exhibited a detectable level of alcohol. These studies provide evidence that a systemic dose of ethanol is likely to be very low after the use of formulations delivering ethanol to the skin.