Immediate Generalized Skin Reactions in Hypersensitive Guinea Pigs.∗

Immediate generalized skin-reactions following contact with or ingestion of allergens have been observed in humans but not hitherto in animals, although Dienes and Simon1reported a generalized delayed reaction in guinea pigs treated with human serum. No observations of generalized skin-reactions in animals, due to simple chemical substances, have been noted in the literature. It seemed of interest, therefore, to report recent observations of such effects in a number of guinea pigs sensitized to citraconic anhydride, together with the sensitization of guinea pigs to new anhydrides having similar properties.The animals were rendered hypersensitive to citraconic anhydride by a method previously described2and were tested by scratching the skin through a 25% dioxane solution of the same substance, usually at intervals of 2 weeks.It was regularly observed that the more hypersensitive the guinea pig the quicker the onset of the reaction. Animals developing generalized reactions showed within a very few minutes a large local wheal and erythema surrounding the scratch, often several centimeters in diameter. At the same time in both contiguous and remote parts of the skin some pigs showed a diffuse pinkishness apparently accompanied by slight thickening, while others exhibited discrete, urticaria-like wheals with distinct elevation and pinkness. Often some of the old injection-sites on the back flared up at the same time, with marked wheal-formation. The erythema reached a maximum 20 to 30 minutes after the test, following which it gradually faded. Edema associated with reactivated sites and other lesions distant from the original scratch increased for about 2 hours and then also diminished. By the next day all such subsidiary reactions had completely disappeared. In striking, possibly significant contrast to this, the reaction in the vicinity of the scratch after receding to a minimal color and edema in 4 to 5 hours, gradually increased in pinkishness and induration to a second maximum reached about 24 hours after the test.