AND THE ANSWERS ARE . . . Correct Answers are: A, D, and E - chlorhexidine, vecuronium, and thiopental. Comment: Chlorhexidine is a widely used disinfectant in many countries. The incidence of anaphylactic reactions to chlorhexidine may be underestimated. IgE antibody against chlorhexidine has been demonstrated on a number of occasions, and protocols for skin testing (both prick and intradermal) have been published. In addition, serum IgE antibodies against chlorhexidine have also been detected. Anaphylactic reactions to Dextran do not appear to be IgE mediated. IgG antibodies to Dextran have been measured, and cross-reactions between these antibodies to Dextran and to bacterial antigens have also been noted. This implies that Dextran reactions may occur due to a cross-reacting pre-existing antibody against bacteria. Skin tests are not helpful. Morphine reacts with mast cell opioid receptors in the skin to induce mast cell degranulation not mediated via IgE, and therefore skin tests cannot be used to distinguish a sensitized versus non-sensitized individual. Morphine, like codeine, can serve as a positive control for allergy skin tests. In the rare instance in which IgE antibodies against opioids have been identified, they are apparently monovalent and therefore would not, at least theoretically, result in mast cell degranulation through an IgE mediated mechanism. Vecuronium is a muscle relaxant. It is a quaternary ammonium compound and serves as a neuromuscular blocking agent. IgE antibodies have been demonstrated against vecuronium, as they have with other quaternary ammonium compounds, and skin testing protocols have been published. Thiopental has been shown to cause IgE mediated mast cell degranulation as well as produce direct mast cell activation. Therefore, interpretation of the skin tests can be difficult, but at least, based upon published reports, IgE mediated events can occur and therefore skin testing might, in certain circumstances, be helpful. However, tests must be performed with concentrations that do not produce irritant or direct mast cell releasing reactions. Please tell us what you think of this site. © Copyright 1997-2008 American Academy of Allergy, Asthma & Immunology All rights reserved