Rare allergic reactions to drugs and commonly used biological substances.

Most drugs and biological substances are potentially allergenic, and numero us reports of isolated cases or small series of allergic reactions, or pres umed allergic reactions to various substances have been published in the li terature. Rather than presenting an exhaustive review of the medical litera ture, looking for a large number of more or less well documented cases, the authors review cases of rare, but well documented allergic drug reactions (drugs of haemostasis, substances used in haemodialysis, insulin, dye injec tions) and draw attention to unexpected reactions to drugs or biological su bstances (vaccines, immunosuppressants and anticancer drugs, local antisept ics, recombinant drugs), for which the number of reported cases, still rela tively small, could well increase in the ears to come. The diagnostic and p redictive value of immuno-allergological assessments varies considerably fr om one substance to another : it is good for delayed hypersensitivity (DHS) or immediate hypersensitivity (IHS) reactions to heparins, IHS reactions t o formalin, gelatin of vaccines, cyclophosphamide, certain dye injections ( Patent Blue V, local antiseptics (chlorhexidine, mercurochrome) and possibl y recombinant drugs (Engerix B, certain cytokines used as haematopoietic gr owth factors). It is much more doubtful for reactions to protamine, aprorin in, ethylene oxide, insulin, and fluorescein. Finally, some substances rais e particular problems, especially dextran contained in certain BCG vaccines , which can be responsible for anaphylactoid reactions related to anti-dext ran IgG, and certain immunosuppressants (cyclosporin, FK-506), which could exert adjuvant effects on the development and expression of allergic reacti ons to various environmental allergens.