Allergen-specific low-dose immunotherapy in perennial allergic rhinitis: a double-blind placebo-controlled crossover study.

In a double-blind placebo-controlled crossover study, 36 adults with perennial allergic rhinitis were treated with daily subcutaneous injections of inhalant allergens, the doses of which had been predetermined by intradermal testing. The dose chosen for each allergen was the maximum intradermally tolerated dose (MITD) of that allergen, defined as 0.05 ml of the strongest concentration in a 1:5 dilution series which did not produce a positive wheal. Of the 27 who expressed a preference, 21 (78%) preferred the active preparation and six (22%) the placebo (p = 0.006). Significant symptom relief was apparent on an analysis of total rhinitis symptom scores (p = 0.006), nasal blockage (p = 0.02), nasal discharge (p = 0.006), postnasal drip (p = 0.02) and anosmia (p = 0.02). These results support the validity of allergen-specific low-dose immunotherapy using the MITD.