When Canadian coroner Michel Miron announced last month that the death of a 15-year-old Quebec girl allergic to peanuts was not the result of kissing her boyfriend, who earlier had eaten a peanut snack, Miron said he hoped to quell the "phobia" surrounding the tragic incident. Indeed, the worldwide media coverage surrounding Christina Desforges' November 2005 death, probably due to her asthma, illustrated how much medical science still does not know about food allergies – and how much the general public fears unpredictable allergic reactions. Food allergy symptoms can "unfortunately be quite variable," says Dr. Frank Virant, an allergist with Northwestern Asthma & Allergy Center in Seattle, Wash. They can range from a little redness and irritation around the mouth to a swelling of the mouth and throat, vomiting and diarrhea, hives, wheezing, a rapid drop in blood pressure and even death. While medical researchers grapple with the problems of food allergies, it's obvious that the incidents of food allergies are increasing, with the prevalence of peanut allergy in children doubling in just five years. Concern regarding peanut allergies has prompted many airlines to discontinue serving peanuts as a snack, although a reaction caused by simply being in a confined space while fellow passengers eat peanuts would be extremely rare. "For reasons we don't yet fully understand, certain allergens like peanuts, some of the tree nuts, cats, horses, grass and ragweed in certain people much more avidly cause a reaction," Virant says. In fact, peanuts, which are actually a legume, and tree nuts such as walnuts and pecans are two of the most allergenic foods for both children and adults, he says. So what's the deal with peanuts? "If you find out, please let me know," quips Dr. Stephen McGeady, an allergist at Thomas Jefferson University in Philadelphia. He says one frustration with nut allergies has been medicine's inability to help control reactions using immunology. He notes that at least two clinical trials to develop a peanut allergy serum were halted recently because of protocol problems and potential dangers to participants. "I think the consensus was that it just wasn't worth it," he says. "They (participants) did show some increased tolerance of peanuts, but side effects of the shots were just horrendous." In fact, participants in clinical trials for peanut allergies have died. McGeady says anti-IgE biologicals such as Xolair® (generic name omalizumab) have promise. Allergies are caused by a body's overeager immune system attacking the protein in foods; in fact, an allergic antibody called IgE (Immunoglobulin E) is found in people with allergies. Thus, a medication that fights IgE logically might increase tolerance for foods that would normally cause an allergic reaction. Virant says, "Our sort of gut feeling is that, although it may not be curative, it clearly would markedly reduce the risk of a reaction to a food like peanut if the patient were on such treatment. Having said that, it's not approved for that indication yet. Studies are still ongoing." Xolair is already approved for patients with moderate to severe persistent asthma that is triggered by year-round allergens in the air. Unlike most allergies that surface early in life, the peanut allergy rarely goes away. Even with avoiding the food, only 20 percent of peanut allergy sufferers overcome the allergy. "That's quite a bit different from most other foods," Virant says. "We tend to also see that with tree nuts, interestingly enough, and also shellfish. Not surprisingly, those are the three most common adult food allergies." For children, the most common allergies other than nuts are milk, egg, wheat and soy – allergies that tend to decrease and usually disappear with time. "If you avoid egg, why does that go away? What does peanut not tend to go away? And we just don't know," Virant says. McGeady says it's important for children with a family history of allergies to be introduced to new foods one at time, making it easier to determine the cause if a reaction occurs. "If we find that a child is clearly food-allergic, then the general recommendation is no cow's milk for one year, no eggs for two years, and no peanuts or seafood for three years," he says. McGeady adds that mothers who breastfeed should try to avoid those foods, too. "It has become apparent now that there are children who become sensitized to the minute amounts of food proteins that pass through the breast milk from the mother's diet," he explains. "So there are lots of kids we skin test for egg when they're eight months old and they get a big reaction. The parents look at us puzzled and say, 'Well, he's never had eggs.' But did you have eggs while you were nursing him?"