The research, published in the Journal of Allergy and Clinical Immunology, adds to evidence supporting the effectiveness of an oral form of immunotherapy using a rapidly dissolving grass allergen tablet called Grazax.

Immunotherapy, in the form of allergy shots, has long been used to treat hay fever and certain other allergies. Allergies arise from an immune system reaction against a normally benign substance, such as grass pollen. Immunotherapy is designed to help the immune system develop a tolerance for the culprit substance, by exposing the body to tiny amounts of it over time.

Despite its effectiveness, immunotherapy is used only for a limited number of patients, partly due to inconvenience and discomfort. The treatment requires weekly allergy shots for several months, followed by monthly ones for several years.

Because Grazax is given by mouth, where it dissolves under the tongue, it could serve as a simpler, more patient-friendly alternative to immunotherapy injections, according to the authors of the new study, led by Dr. Ronald Dahl of Aarhus University in Denmark.

Based on this study and earlier, preliminary research, Grazax has already been approved in Sweden. The product maker, Denmark-based ALK-Abello, is now applying for approval in other European countries.

The data supporting the effectiveness of Grazax come from 634 adults with grass pollen allergy who were randomly assigned to take either a Grazax pill or a placebo pill every day, starting at least 16 weeks before the allergy season, then continuing throughout the season.

Each day, the patients used a scale to rate the severity of their symptoms, including runny nose, congestion, sneezing and itchy, watery eyes.

Overall, Dahl's team found, patients on immunotherapy had symptom scores that were 30 percent lower than placebo patients', and they needed their standard hay fever medication about one-third less often. The immunotherapy group also had more symptom-free, medication-free days during allergy season.

Side effects of the treatment included throat irritation and itchiness and swelling in the mouth and ears. But the researchers found no instances of serious allergic reaction to the therapy, which can sometimes happen with allergy shots.

"The grass allergen tablet," Dahl and his colleagues conclude, "might represent a new baseline treatment of grass pollen allergy."

Ongoing research will look into whether the benefits last once patients stop taking the pills, after a few years of treatment. ALK-Abello is funding the research, and several of the study authors have financial ties to the company.