Behavioral conditioning of antihistamine effects in patients with allergic rhinitis

Allergic symptoms can be induced by behavioral conditioning. However, the conditionability of antiallergic effects has not yet been studied. Thus, we investigated whether the effects of a histamine 1 (H(1)) receptor antagonist are inducible in patients suffering from house-dust mite allergy using a behavioral conditioning procedure.

During the association phase, 30 patients with allergic house-dust mite rhinitis received a novel-tasting drink once daily, followed by a standard dose of the H(1) receptor antagonist, desloratadine, on 5 consecutive days. After 9 days of drug washout, the evocation trial commenced: 10 patients received water together with an identically looking placebo pill (water group), 11 patients were re-exposed to the novel-tasting drink and received a placebo pill [conditioned stimulus (CS); CS group] and 9 patients received water and desloratadine (drug group).

During the association phase, desloratadine treatment decreased the subjective total symptom scores, attenuated the effects of the skin prick test for histamine and reduced basophil activation ex vivo in all groups. During the evocation trial, the water group, in which subjects were not re-exposed to the gustatory stimulus, showed a reduction in subjective total symptom scores and skin prick test results, but no inhibition of basophil activation. In contrast, re-exposure to the novel-tasting drink decreased basophil activation, the skin prick test result and the subjective symptom score in the CS group to a degree that was similar to the effects of desloratadine in the drug group.

These data show that behaviorally conditioned effects are not only able to relieve subjective rhinitis symptoms and allergic skin reactions, but also to induce changes in effector immune functions.