Vegetables responsible for contact dermatitis of the hands.

Fifty-three patients having contact dermatitis on the fingertips showed positive patch tests with several vegetables the commonest being garlic, onion, tomato, and carrot in that order of frequency. Of several preparations, made from garlic onion, tomato, and carrot, the juices used as such gave the maximum number of positive patch test reactions. Lyophilization of the juices led to false-negative patch tests in some cases. Patch tests in the controls were positive in some cases but these were probably cases of latent hypersensitivity, because some of them, like the patients, showed positive reactions even with the diluted juices. The antigens in garlic and onion were extractable in water, ether, acetone, or alcohol and were also present in the essential oils of these vegetables. Infrared spectra of the essential oils of garlic and onion were similar and showed straight chain acids, esters, and methylene groups. Clinically, there was no suggestion of cross-sensitivity between onion and garlic.