For nine-year-old Priya, a single bite of peanuts could provoke a dangerous allergic reaction.

"I can't have it because I don't want to take the chance," she said.

For her dad Kam, the threat of the allergy is a constant stress.

"We don't know where it will come from. Will a responsible person be around to give her treatment or call 911?"

But a new therapy may offer hope to Priya and the thousands of Canadian adults and children with severe peanut allergies, researchers announced Monday.

The experimental treatment involved injections of the first antibody to successfully lessen the reactions of people highly allergic to the slightest amount of peanut protein.

"It's very intersting. It shows some promise, but for now it's an experimental tool," said Dr. Ron Filderman, an allergy specialist.

The study looked at the reactions of 82 patients with severe peanut allergies who received four monthly shots of the drug TNX-901. The drug is a humanized antibody against IgE, which is the substance that tells immune cells to release histamine, the chemical that initiates allergic reactions.

Of those receiving the highest dose of TNX-901, 450 mg, the treatment cut sensitivity to peanuts in 76 per cent of the volunteers.

Researchers found that the drug raised the threshold of sensitivity from an average level equal to about half a peanut (178 mg of peanut flour) to one equal to almost nine peanuts (2805 mg).

Nine peanuts may not sound like much, but the researchers say that kind of effect would translate into protection against most unintended ingestions of peanuts.

And nearly a quarter of the patients receiving the highest dose of TNX-901 could consume 8,000 mg, or about 24 peanuts, with no reaction.

"Our results indicate that the anti-IgE antibody could become the first preventive medicine for peanut allergies," said Dr. Donald Leung, a co-leader of the research team. "If future studies bear out this initial promise, anti-IgE could not only save lives, but help lift a cloud of fear that people with peanut allergies live under every time they eat."

The study results are being presented to the American Academy of Allergy, Asthma and Immunology and will be published in this week's New England Journal of Medicine.

Food allergies on the rise

For reasons not understood, peanut allergies have doubled in Canada in the last decade, with one in 100 Canadian children now being diagnosed with the allergy. Allergic reactions can include anything from nausea, to anaphylactic shock, to death.

The allergy can be so severe that people have been known to develop symptoms after eating just 1/2,000th of one peanut or kissing someone who has eaten peanuts. Researchers estimate that most fatal reactions occur after an allergic person accidentally eats the equivalent of just one to two nuts.

Scientists have experimented with traditional allergy shots in the past for those with peanut allergies, but the rate of side effects has been too high. Those with the allergy can do little to protect themselves except avoid all peanut traces or use epinephrine to control a reaction.

The researchers say that although these results are highly encouraging, they believe the drug would not be a cure and that patients would have to continue the injections for life, for the benefits to persist.

"We believe that patients... still would need to be careful about what they eat," said Dr. Hugh Sampson, another co-leader of the research team. "But, because the amount they could consume without serious reaction would be greatly increased, the fear of accidental ingestion that detracts from quality of life for many patients would be eliminated.

"These are very promising results."

It's hoped that the treatment may be useful for other types of food allergies, helping those allergic to eggs, cats, dogs, and other types of nuts, according to the study.

TNX-901 is still an experimental drug, and approval for general use will require more studies, the study authors warn.

Despite this good news, further development of the drug is now in limbo because of a convoluted dispute over the rights to it between the developer, Tanox, and its two much larger partners, Genentech and Novartis.

The other issue is the cost of these treatments, an estimated $14,000 per year.

But despite the cost, it could buy families and allergy sufferers like Priya something they don't have now. "Peace of mind for us. Peace of mind for her and for anybody who interacts with her," said her dad, Kam.