["Iodine allergy": point of view].
OBJECTIVE
The aim of this literature review is to suggest a diagnostic and a preventive attitude in patients having presented an immediate hypersensitivity reaction due to an iodinated drug.


METHODS
Literature review. Data were searched in the Medline database from 1967 to 2004 in English and French language. Complementary references were selected from the bibliography of selected references or from authors' personal databases. The following key-words were used separately or combined: Hypersensitivity, Immediate; Allergy; Contrast Media; Povidone-Iodine; Iodine; Iodine Compounds; Iodides; Amiodarone; Seafood, Parvalbumins; Tropomyosin.


METHODS
Randomized studies, epidemiological studies, original articles, clinical cases, and letters to the editor were selected.


RESULTS
The implication of iodine has never been demonstrated during allergic hypersensitivity reactions due to iodinated drugs. However, IgE-mediated allergic hypersensitivity reactions have been published with contrast media or iodinated antiseptics and will be described in this development. In a wider sense, allergic hypersensitivity reactions due to seafood are evoked because often improperly considered as a risk factor of allergic reaction to iodinated drugs. The allergenic determinant responsible of patient sensitization is not known for iodinated contrast media, but is probably due to povidone in case of iodine povidone. In fish, the allergen is described as the protein M. There has also been strong immunological evidence that tropomyosin is a cross-reactive allergen among crustaceans and molluscs (shellfishs). In case of hypersensitivity reaction occurring with iodinated drug, an allergological assessment is required to confirm the immune mechanism, to identify the culprit drug or substance and to identify cross-reactivity especially with iodinated contrast media.


CONCLUSIONS
Asking a patient if he/she is "allergic to iodine" is a question that should be avoided because its significance is null. A diagnosis of drug allergy, essentially relying on clinical symptoms, biological tests and cutaneous tests, is required to take adequate preventive measures.
Dewachter
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P
Service d'anesthésie-réanimation chirurgicale, CHU, hôpital central, 29, avenue du Maréchal-de-Lattre-de-Tassigny, 54035 Nancy cedex, France. pascale.dewachter@wanadoo.fr
Tréchot
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P
Mouton-Faivre
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C
D000891:Anti-Infective Agents, Local / Q000009:adverse effects; D003287:Contrast Media / Q000009:adverse effects; D004342:Drug Hypersensitivity / Q000453:epidemiology / Q000276:immunology / Q000517:prevention & control / Q000628:therapy*; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000276:immunology; D007073:Immunoglobulin E / Q000276:immunology; D007455:Iodine / Q000009:adverse effects*
D000891:Anti-Infective Agents, Local; D003287:Contrast Media; D007073:Immunoglobulin E; D007455:Iodine