title: [Urticaria paradoxically aggraved by H1 antihistamines].
abstract: BACKGROUND
  H1 antihistamines (anti-H1) are the treatment of choice in chronic urticaria. We report five cases of urticaria, induced or aggravated by H1 antihistamines.
  
  
  METHODS
  The immunoallergological investigations included prick-tests and intradermal tests with the antihistamine responsible for acute urticaria.
  
  
  RESULTS
  The skin tests confirmed the non-IgE dependent nature of the urticarial eruptions and anti-leukotrienes (montelukast, Singulair) were effective in controlling chronic urticaria in 3/4 patients.
  
  
  CONCLUSIONS
  Two hypotheses are discussed to explain the paradoxical aggravating effect of H1 antihistamines on the urticaria: 1) the patients are sensitive to the toxic, pro-inflammatory effect of the drug, which is the source of nonspecific activation of mast cells; 2) the fact that the urticaria is sensitive to anti-leukotrienes suggests that histamine is not the principal mediator of urticaria in these patients.
authors.affiliation: Unité Immunologie Clinique et Allergologie, CHU Lyon-Sud, et INSERM U 503, IFR 128, 69495 Pierre-Bénite Cedex, Lyon, France. amandine.lamy-catelain@chu-lyon.fr
authors.forename: A
authors.initials: A
authors.lastname: Catelain
authors.forename: N
authors.initials: N
authors.lastname: Freymond
authors.forename: E
authors.initials: E
authors.lastname: Queuille
authors.forename: J-F
authors.initials: JF
authors.lastname: Nicolas
mesh_terms: D000328:Adult; D005260:Female; D006634:Histamine H1 Antagonists / Q000009:adverse effects* / Q000627:therapeutic use; D006801:Humans; D008297:Male; D008875:Middle Aged; D012720:Severity of Illness Index; D014581:Urticaria / Q000139:chemically induced* / Q000188:drug therapy*
chemical_list: D006634:Histamine H1 Antagonists