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Histamine is an important mediator for early phase allergic reactions that are involved in atopic diseases, mediated by specific IgE antibodies. After allergenic contact, its liberation induces unpleasant symptoms like itching, several manifestations as local vasodilatation, bronchoconstriction, mucus hypersecretion. Antagonists of H1 histamine receptors are the most prescribed drugs, due to their symptomatic effects at the levels of nasal or conjunctival mucosa, and the skin. Their major indications cover allergic rhinitis, either seasonal or perennial, and idiopathic chronic urticaria, as a first line medication. The pharmacological evolution allows to distinguish three generations of products differing at the levels of specificity, long acting period, and toxicity. The authors are discussing the respective benefits of two recent molecules presented as 3rd generation molecules: fexofenadine and levocetirizine, while repositioning their use among available treatment strategy.

Fifty eight patients with rhino-conjunctivitis caused by grass pollen were included in a double-blind study in which they received, by the sub-lingual route over 5 months, either a solution of purified and standardised allergen or a placebo. Assessment of the effect of this immunotherapy, which was done with drops of Stallergenes "5-grass pollen" was by clinical symptoms and the use of authorized drugs and treatments. Compared with the placebo group, the patients on active treatment showed significantly less (P = 0.05 to P = 0.01) rhinitis symptoms (sneezing and rhinorrhea) and conjunctivitis (reddening and tears) during the pollen season. Consumption of nasal cromoglycate solution, of betamethasone and dexchlorpheniramine was significantly lower (p = 0.01) in the desensitised group. Secondary effects were negligible. From this study, it can be concluded that immunotherapy with grass pollen extract, by the sub-lingual route, of patients with rhino-conjunctivitis who were sensitive to these allergens, is efficacious, easy to do, economic and sure.

Our randomised study in parallel groups, double-blind double placebo, has compared the efficacy, onset of action and safety of terfenadine and cetirizine in chronic idiopathic urticaria. Over a fourteen day period, patients of the first group received a tablet containing 120 mg of terfenadine, those of the second group a tablet containing 10 mg of cetirizine. Symptoms were assessed every two hour period for the ten first hours on the first day (D1), and before and at the end of the study by the investigators. 193 patients were included by 48 dermatologists between May 1989 and July 1990. Both groups were well matched for all general characteristics and baseline symptoms scores. The onset and the intensity of regression of symptoms (pruritus, erythema and discomfort during sleeping time) were similar in both treatment groups public physicians: improvement of pruritus in over 90% of the patients. Meanwhile the tolerability was good or excellent for dermatologists and allergologists for 92% of the patients under terfenadine against 81% of the patients under cetirizine (p < 0.05). Adverse events (fatigue and drowsiness) were significantly reported less frequently (p < 0.05) in patients on terfenadine (19%) than on cetirizine (33%). This study confirms the efficacy of terfenadine compared with cetirizine in the treatment of chronic idiopathic urticaria. Adverse events were less significant for terfenadine (n = 18) than for cetirizine (n = 29) (p < 0.05).