Induction of human skin sensitization to ethanol

In predictive skin sensitization tests, 50% aqueous ethanol induced delayed allergic skin reactivity in 6 of 93 human volunteers. This was confirmed 2 months after the primary challenge by producing an allergic response in each of the 6 with a single 24-hr application of 50% aqueous ethanol. Three of these reactive subjects also responded to lower concentrations of ethanol in water, and 2 of them still showed allergic reactivity 18 months later. Possible allergens other than the ethanol itself (i.e., an impurity or an ethanol-soluble component of the patch) were eliminated. Responses of 1 subject to ethanol that had been purified by gas chromatography confirmed that ethanol alone was the sensitizer. This subject also reacted to other short-chain primary alcohols, a secondary alcohol, and acetaldehyde, suggesting an antigenic relationship among all of these compounds in the skin. One of the authors, who had become sensitized to acetaldehyde, showed a similar pattern of cross-reactivity. Previous infrequent reports of ethanol sensitivity have been limited to case studies and diagnostic patch testing. This work provides evidence that a test designed to predict skin-sensitizing potential will identify even a weak sensitizer such as ethanol. Aqueous ethanol solutions approaching 50% concentrations should be avoided as vehicles in human predictive sensitization testing.