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Allergy sufferers may soon breathe a little easier

A minute after 8-month-old Stefan Lainovic swallowed a quarter-teaspoon of yogurt, hives broke out on his face and he struggled for breath. A dose of Benadryl stabilized him, but doctors warned his parents to be vigilant: It seemed the slightest amount of milk or eggs could send their son into anaphylactic shock, causing him to lose consciousness and potentially die.

“There was nothing definitive that said he was anaphylactic,” recalled his mother Rebecca Lainovic. “But the doctors said, ‘Wow, he is wildly allergenic."

So Stefan’s parents began closely monitoring his diet. Most of the time, Rebecca Lainovic makes her son’s meals before he goes out because restaurant food poses too many risks. Even egg- or dairy-free dishes that briefly come in contact with these ingredients during preparation can cause a severe allergic reaction.

Allergies from foods to insects to medications may no longer need to be a game of trial and error, though. Researchers in Toronto say they may have discovered a way to determine whose allergies could be fatal, and whose will just be unpleasant.

The study, published in January in The New England Journal of Medicine after seven years of research, shows that people who suffer severe allergic reactions such as anaphylactic shock consistently have high levels of a particular chemical, called platelet activating factor or PAF, in their bloodstream, and low levels of the enzyme PAF acetylhydrolase. It found that this enzyme inactivates the PAF chemical in humans. In other words, patients have to have low levels of this enzyme for life-threatening allergic reactions to occur.

“It’s like a Western,” said lead researcher Dr. Peter Vadas, director of the Division of Allergy and Clinical Immunology at St. Michael’s Hospital in Toronto. “PAF acetylhydrolase is the good guy fighting off PAF, which is the bad guy.”

As a result, says Vadas, doctors may soon be able to tell allergy sufferers like Stefan, now 15, with certainty how serious their reactions to particular allergens could be. They could warn at-risk patients to be extra careful and calm the fears of patients who will not experience life-threatening reactions.

And the study could affect a lot of people. According to the National Institute of Allergy and Infectious Diseases, about half of all Americans have positive skin tests for at least one of the 10 most common allergens, including peanuts, cats and house dust mites. Reactions can range from itchiness to vomiting to the most extreme, anaphylactic shock. Between 500 and 700 Americans die each year from contact with latex, insect stings, penicillin and various types of food.

Up to now, doctors have diagnosed the severity of the allergy based primarily on anecdotes: They look at whether the patient is asthmatic, as most people who die from an allergic attack are, and at past allergic reactions, which aren’t always reliable. For example, patients will sometimes tell their physicians they have experienced a severe attack when they’ve had only a relatively minor outbreak of hives, said Dr. Steve Taylor, who studies food allergens as co-director of the Food Allergy Research and Resource Program at the University of Nebraska-Lincoln.

As a result, said Vadas, doctors are very cautious. Some patients who don’t really need it are advised to carry an autoinjector of epinephrine like an EpiPen, which provides temporary relief during anaphylaxis.

“We end up treating everybody the same way,” he said. This concerns some industries that are frequently associated with severe allergic reactions. The National Peanut Board, which represents all peanut growers in the United States, has put about $4 million toward food allergy research, including $200,000 for Vadas’ recent study since 2001.

“At its founding, the board determined that if one person is ever harmed by its product, it is one too many,” said Lisa Agostoni, a spokesperson for the National Peanut Board.

Vadas is waiting until further research confirms the study’s conclusions to test it on his own patients. In the future, he hopes that the study will allow doctors to more accurately treat their patients and perhaps lead to an allergy cure.

“Now having identified that PAF seems to cause more severe reactions allows us to target PAF in a very specific way as a new type of therapy,” he said.

Other allergen researchers see Vadas’s work as very encouraging. Said Dr. Marshall Plaut of the National Institute of Allergy and Infectious Diseases, “If the implications of the study are what they appear to be, then this could be a major breakthrough for understanding anaphylaxis.”

E-mail: msl2003@columbia.edu