Safety of sublingual-swallow immunotherapy in children and adults

Background: Immunotherapy is an established treatment of allergic diseases. The safety of this treatment, particularly when administered without direct medical surveillance, as in the case of the sublingual-swallow route needs to be established. The aim of this paper is to review the safety of the sublingual-swallow immunotherapy as reported in eight double-blind, placebo-controlled trials carried out in France, Italy and Greece.

Methods: Six hundred and ninety subjects, 472 adults and 218 children, took part in trials of specific immunotherapy (SIT) for the treatment of rhinoconjunctivitis and/or asthma. Three hundred and forty-seven patients received SIT and 343 patients received placebo. Treatment with specific immunotherapy with allergen extracts or placebo was administered using the sublingual-swallow technique. The allergens administered were grass, ambrosia, parietaria and olive pollens, and mites. The daily dose taken during maintenance therapy ranged from 100 to 300 IR (index of reactivity) and cumulative doses ranged from 4,500 to 104,000 IR. Treatment duration ranged from 4 months to 2 years. Adverse events reported either spontaneously by the patient or on direct questioning by the investigator were analysed.

Results: One hundred and forty-five unusual events were reported in the subjects receiving active SIT and 79 in those receiving placebo (p < 0.001). Of these 85 were children aged 15 years or less (50 received active SIT, 35 placebo) and 139 were adults (95 received SIT, 44 placebo). Unusual events involving the buccal cavity (61 SIT, 13 placebo) and the gastro-intestinal tract (47 SIT, 15 placebo) were significantly more frequent in the SIT-treated patients (p < 0.001). Wheezing (9 SIT, 21 placebo) was more frequent in the placebo-treated patients (p < 0.05). There were no differences in the frequency of unusual events between adults and children and in the frequency of events involving other body systems. No event was reported as serious. Two events reported as laryngeal oedema were not considered to be accurate descriptions.

Conclusions: No serious adverse event was reported in the studies monitored, confirming the good safety profile of the sublingual-swallow method both in children and adults with rhinitis or moderate asthma.