Allergy shots safe, effective for hay fever

NEW YORK (Reuters Health) - Allergy shots are a safe, effective way to relieve hay fever symptoms, UK researchers have concluded after reviewing 51 studies comparing the therapy to a placebo.

But the injections must be performed in a physician's presence and by personnel experienced in recognizing and treating severe allergic reactions, Dr. Moises A. Calderon of Royal Brompton Hospital in London and colleagues conclude.

Known medically as seasonal allergic rhinitis, hay fever is an allergic reaction to pollen from trees, grasses or weeds that leads to sneezing, runny nose and watery eyes. Allergy shots are recommended for people whose hay fever can't be treated effectively by medicine. They consist of extracts of the allergy causing substance (allergen) via injections under the skin. The amount of the allergen is gradually increased until a maximum dose is reached, which is followed by maintenance shots for as long as several years.

While the shots are considered effective, there have been concerns about their safety due to the potential of a severe immune reaction. The shots are not recommended for people with asthma, who are at greater risk of severe reactions to immune therapy.

To get a clearer picture of the risks and benefits of allergy shots for hay fever, Calderon and his team evaluated 51 high-quality studies including 2,871 participants. Patients received an average of 18 injections, and were treated for periods ranging from three weeks to three years.

The trials showed a reduction in symptoms for patients given immunotherapy, as well as a reduction in the amount of medication necessary to control symptoms. There were no fatalities, while adrenaline therapy was necessary to treat a severe immune reaction in 19 of the 14,085 injections given during the studies.

"We can consider that the risk/benefit ratio of injection immunotherapy favors treating patients with seasonal allergic rhinitis who have not responded to standard drugs, provided that potential risks and benefits are properly assessed and explained to the patient," the researchers conclude.

SOURCE: The Cochrane Library, January 25, 2007.