Immunotherapy with sublingual birch pollen extract. A short-term double-blind placebo study

The aim of this double-blind placebo-controlled study was to evaluate the efficacy and tolerability of short-term birch pollen sublingual immunotherapy. Forty-one patients suffering from allergic rhinoconjunctivitis caused by Betula alba were included. Exclusion criteria were the following: undergoing immunotherapy within the last 2 years, contraindications to immunotherapy, pregnancy and nursing. The treatment schedule comprised a 28-day basic course, followed by a 3-month maintenance treatment. The evaluation of the parameters was performed before treatment and 4 months after the last maintenance dose. Skin prick test and conjunctival provocation test (CPT) in a dilution series were carried out to determine the threshold of the reaction. The objective parameters used were the diameter of the skin wheals and the lowest concentration, of the allergen extract to induce the symptoms of itching and reddening of the eyes. The allergic reaction in general was evaluated with the help of a 2-h birch pollen challenge in the Vienna Challenge Chamber (VCC); nasal flow and resistance was measured by rhinomanometry; and nasal secretion was quantified by weighing used handkerchiefs. Bronchial reactions were objectified by spirometry; subjective symptoms of the eyes, the nose and the bronchial tract were documented by the patients via a visual analog scale. Birch pollen specific IgE and IgG were evaluated by monoclonal antibody enzyme immunoassay before (T0) and after (T1) treatment. For statistics p < 0.05 was applied. At T0 there was no decisive difference in the in vitro and in vivo results between the two groups. After the treatment period (T1), actively treated patients showed a significantly higher tolerance to the birch pollen CPT (p < 0.01). The skin reaction was significantly lower than in the placebo group. Furthermore, actively treated patients produced less than half of the nasal secretion of placebo-treated patients during the challenge session. The rhinomanometry analysis during the challenge showed significant differences for verum and placebo in favor of the actively treated patients (p = 0.033). There was no significant difference in the specific IgE and IgG concentrations. The side effects and compliance during the treatment were comparable in both groups. In conclusion, sublingual immunotherapy is a well tolerated and clinically effective method of treatment.