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The chemical reactivity of contact allergenic dinitrohalobenzenes in the skin following skin contact, ostensibly via a nucleophilic aromatic substitution reaction with amino groups on proteins, was originally described by Landsteiner and Jacobs in 1936 [1] and subsequently established as fact in the minds of a generation of dermatologists when the reaction was described in a text book published by Dupuis & Benezra in 1982 [2]. When the biochemical reactivity of the various halonitrobenzenes investigated by Landsteiner & Jacobs was subsequently studied by Schmidt & Chung in 1982 [3] using in vivo and ex vivo systems [mouse skin and rat liver], the notion that nucleophilic aromatic substitution reactions could explain the experimental observations had to be questioned – except perhaps in the case of dinitrofluorobenzene and picryl chloride. Instead, the observed biochemical reactions of contact allergenic nitrohalobenzenes could be better explained in terms of NADPH-dependent one-electron nitroreductase activity in the skin generating potentially haptenic carbon-centred free radical species.

[1] https://doi.org/10.1084/jem.64.4.625
[2] Dupuis G, Benezra C (1982) Allergic contact dermatitis to simple chemicals. A molecular approach. Marcel Dekker, New York.
[3] https://doi.org/10.1007/BF00372070