NEW YORK (Reuters Health) – Children who suffer from hay fever, due to allergies to mould or pollen, are less likely to go on to develop asthma if they get immunotherapy to combat their sensitivity to allergy-triggers, researchers say.

Immunotherapy aims to build up tolerance to substances that set off allergic reactions by slowly exposing the affected person to gradually increasing doses of the allergen, either by injections or administration under the tongue. The process can take months or years to achieve full desensitisation.

The current study, a follow-up of the Preventive Allergy Treatment (PAT) study, showed that specific immunotherapy for children with hay fever, or "seasonal allergic rhinoconjunctivitis'', helps prevent the development of asthma for up to seven years after treatment ends.

The PAT study investigated whether the effects of three years of immunotherapy persist in children with seasonal allergic rhinoconjunctivitis caused by birch and/or grass pollen allergy as they grow up. The results at ten years after the start of treatment are reported in the medical journal Allergy.

Dr. L. Jacobsen from ALK-Abello, Horsholm, Denmark and colleagues found that, among 117 children who were free of asthma at the start of the study, those given immunotherapy were 4.6 times more likely than those treated with an inactive "placebo" to remain free of asthma during the ten years of follow-up.

Of 53 patients given placebo, 24 developed asthma, whereas among the 64 patients in the immunotherapy group, 16 became asthmatic.

Furthermore, the beneficial effect of immunotherapy in easing allergy symptoms, like runny noses and itchy eyes, also persisted seven years after completion of three years of treatment.

"This ten-year follow-up study demonstrates that specific immunotherapy for three years with high-dose standardised allergen extracts shows persistent long-term effect on clinical symptoms after termination of treatment and long term, preventive effect on later development of asthma in children with seasonal rhinoconjunctivitis," Jacobsen's team concludes.

"In this light," they write, "specific immunotherapy should be recognised not only as first line therapeutic treatment for allergic rhinoconjunctivitis but also as secondary preventive treatment for respiratory allergic disease."