Allergen exposure 'cuts asthma risk'
17 August 2007

Children who have hay fever caused by allergies to mould or pollen are less likely to develop asthma if they receive treatment to combat their sensitivity to allergy-triggers, according to Danish researchers.

The treatment, called immunotherapy, aims to build up tolerance to substances that set off allergic reactions by gradually exposing the affected person to the allergen. The process can take months or years to take full effect.

The current study is a follow-up to the Preventive Allergy Treatment (PAT) study, which began 10 years previously and lasted for three years. The PAT study investigated whether the effects of three years of immunotherapy would remain in children with hay fever caused by birch and/or grass pollen allergy as they grow up.

It showed that specific immunotherapy for children with hay fever helps prevent the development of asthma for up to seven years after treatment ends.

The researchers found that, among 117 children who were free of asthma at the start of the study, 16 of the 64 children given immunotherapy remained free of asthma, whereas 24 of the 53 children given an inactive ‘placebo’ developed symptoms of asthma during the following 10 years.

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.

Dr Victoria King, Asthma UK’s Research Development Manager, said: This study suggests that immunotherapy during childhood for hayfever symptoms may have the potential to reduce the development of asthma in some people seven years after treatment had finished. Immunotherapy has previously been shown to reduce asthma symptoms, but the size of the benefit compared to other therapies has not yet been fully determined; it would therefore be beneficial to compare established drug therapies with immunotherapy in their ability to influence the establishment of long-term asthma in adults.’