Mechanism of allergic contact dermatitis from propacetamol: sensitization to activated N,N-diethylglycine.

In order to confirm the mechanism of skin sensitization to propacetamol, a pro-drug of acetaminophen, 3 patients with allergic contact dermatitis from propacetamol were patch tested with N,N-diethylglycine phenyl ester, an activated form of N,N-diethylglycine. Positive patch tests were observed in all the patients at 10% in pet., while 20 control patients remained negative. This strongly suggests that propacetamol is acting as an activated form of N,N-diethylglycine, transferring this part of the molecule to nucleophilic residues of proteins. This also explains why reactions to acetaminophen have never been observed in patients sensitized to propacetamol.