[Immediate hypersensitivity is rarely implicated in drug induced urticaria].
BACKGROUND
The unexpected appearance of acute urticaria during the course of drug treatment gives rise to the following question: is it an allergic urticaria (due to an immediate hypersensitivity: IgE mediated specific immunity) or is it pseudo-allergic? We report our findings in an immuno-allergological study of patients who were sent for drug intolerance which presented as immediate hypersensivity (urticaria, angiooedema, anaphylactic shock).


METHODS
A prospective study was conducted including all the patients who were sent to the unit for urticaria or angiooedema type drug intolerance. Patients were questioned about previous chronic urticaria and also about urticaria after taking different medicines. The clinical examination looked for a dermographism. All the patients then took skin tests for immediate hypersensitivity, the molecule was contra-indicated and tests for cross-reactivity were conducted.


METHODS
Three hundred fifty patients were sent to this unit between February 2000 and April 2001 for drug intolerance, mostly with urticaria/angiooedema but in 7 cases with anaphylactic shock. The incriminated drugs were varied: 50 p. 100 were due mainly to penicillins and cephalosporins. Other drug groups were also involved: non steroid anti-inflammatories, aspirin and paracetamol for the most part, along with local anesthetics, morphine-based products, contrast iodine products, corticosteroids.


RESULTS
Of the 350 patients tested, only 22 were allergic and had positive tests for the incriminated drug. In these 22 patients, with the exception of 2 of them, the effects were severe (anaphylactic shock in 7 patients) and the urticaria was only a minor manifestation of the reaction. The drugs responsible were cephalosporin (10 patients), the penicillin (6 patients), insulin (2 patients), gonadorelin (1 patient), carboxymethylcellulose (1 patient), lidocain (1 patient), and sulfamethoxazole (1 patient). The 328 other patients had negative tests and were able to retake the tested molecule without incident. Most of them had antecedents of chronic urticaria or dermographism.


CONCLUSIONS
Only 22 patients of the 350, i.e. 6 p. 100 were genuinely allergic. These patients were those who presented the most severe symptoms. The other patients, i.e. the majority, suffered from pseudo-allergic drug-induced urticaria, which made retaking the medicines possible.
Unité d'Immunologie Clinique et Allergologie, Centre Hospitalier Lyon Sud, 69495 Pierre-Bénite Cedex.
F
F
Cousin
A
A
Catelain
K
K
Philips
B
B
Favier
E
E
Queuille
J-F
JF
Nicolas
D000707:Anaphylaxis / Q000139:chemically induced / Q000276:immunology; D000799:Angioedema / Q000139:chemically induced; D004342:Drug Hypersensitivity / Q000276:immunology*; D005189:False Positive Reactions; D006801:Humans; D011379:Prognosis; D011446:Prospective Studies; D012882:Skin Tests; D014581:Urticaria / Q000276:immunology*