Effects of specific immunotherapy on the development of new sensitisations in monosensitised patients.

BACKGROUND Specific immunotherapy (SIT) is the only treatment that interferes with the basic pathophysiological mechanisms of allergic disease and is widely used in the management of clinically significant respiratory IgE-mediated diseases. Nevertheless, until recently, information on the influence of SIT on the development of new allergic sensitisations has been scant. METHODS One hundred consecutive patients (45 males and 55 females, aged 6 to 69 years) with respiratory allergic diseases and attending the allergy unit of a general hospital were selected. All had been diagnosed by clinical history and skin prick tests of allergic rhinitis and/or asthma, were monosensitised (71 to Dermatophagoides spp, 22 to Parietaria judaica pollen and 7 to grass pollen) and had been followed up as outpatients between 1990-98. Sixty-six patients had been treated with conventional SIT for at least 3 years, while thirty-four followed only environmental measures and drug treatment. Family atopy status (first-degree relatives), smoking, family pets (cat and/or dog), rhinitis and/or asthma symptom score and inhalant skin prick tests to the same aeroallergens were compared between baseline and after 3 to 5 years of treatment. RESULTS No statistically-significant differences in the development of new sensitisations were observed between the two groups (36.4 % of SIT-treated patients versus 38.2 % in control group, RR = 0.97, CI 95 %: 0.72-1.3). Smoking, family atopy history and pets did not appear to be risk factors for the development of neosensitisations (p < 0.05). Nevertheless, SIT-treated patients presented a better clinical score than the control group, with improvements of 89.4 % and 61.8 %, respectively (p = 0.007). CONCLUSIONS Three-year SIT did not protect against development of new sensitisations in monosensitised allergic rhinitis or asthma. Smoking, family atopy history and pets were not associated with development of new sensitisations. Clinical score improved significantly in the SIT-treated group compared with drug-treated patients.