An experimental treatment for peanut allergies is showing promise, according to a new study.

A report in the New England Journal of Medicine says monthly injections of the new treatment have muted the reactions of people who are allergic to peanut protein.

About two per cent of people can have an anaphylactic reaction to an allergen usually nuts or seafood.

Anaphylactic shock is an explosive overreaction of the body's immune system. It starts with swelling, difficulty breathing, cramps, vomiting, diarrhea and can proceed to coma and death.

Researchers recruited 84 people who had peanut allergies. They were randomly assigned to receive either a placebo or one of three doses of TNX-901 four times at four-week intervals.

Researchers found there were no serious adverse effects of the drug except for one person who had hypertension and had to be hospitalized.

All were tested for their allergy within four weeks of the last treatment.

The volunteers were able to eat an average of eight peanuts before experiencing symptoms of their allergy. Others ate as many as 24 peanuts.

TNX-901 is able to block the chemical pathway responsible for food allergies. The treatment could help in people allergic to other things such as cats, eggs and other nuts.

Patients who received the highest dose of the drug showed the largest improvement. The treatment cut sensitivity to peanuts in 76 per cent of the participants.

"Some patients have reported that they seem to have also developed a greater tolerance to foods other than peanuts," said Hugh Sampson, the study's co-author, in the journal report.

Final testing on the treatment is now being held up by litigation among the three companies that developed the drug &3151; Tanox, Genentech and Novartis.

The treatment could be on the market in four years if the three companies settle soon.

The study was paid for by Tanox, the Peanut Foundation and the U.S. National Institutes of Health.