Food allergy: analyzing fatal reactions.

It's common knowledge that for people allergic to bee venom, a simple sting can bring death. Less well appreciated -- both among physicians and the public -- is that food allergies can also kill, and they appear to be on the rise. Indeed, they may now claim more lives than insect stings among children and adolescents, according to data from a new study

In reviewing the course of life-threatening reactions to food in 13 children, six of whom died, the researchers turned up several surprises, including signs of an increased risk of severe reactions in food-allergy sufferers with asthma.

Their findings also strongly suggest that all food-induced reactions involving respiratory symptoms, such as trouble breathing, deserve respect- and a visit to the hospital, says study coauthor Hugh A. Sampson of Johns Hopkins University in Baltimore. In three to four hours, reactions that initially appeared mild to moderate can turn deadly, his team reports in the Aug. 6 NEW ENGLAND JOURNAL OF MEDICINE.

Allergists tend to expect that in cases where reactions will prove severe, symptoms will progress rapidly, probably within 30 minutes of allergen ingestion. But Sampson notes that three of the children who died had recovered from early symptoms for an hour or two before suddenly entering a catastrophic phase.

The protracted nature of some reactions also surprised his team. One young girl, Sampson notes, "spent three weeks on a ventilator with all the major suppressor drugs before she came through."

One thing common to all children in the study was asthma, a disease that can have allergic underpinnings. This "provocative" finding certainly hints that asthma "may be a risk factor for death from food allergy," says Marshall Plaut, asthma and allergy branch chief at the National Institute of Allergy and Infectious Diseases in Bethesda, Md.

Plaut was also surprised to learn that concentrations of the enzyme tryptase were not elevated in the blood samples taken from two of the children with food allergies (one of whom died). Tryptase elevations typically characterize severe reactions to other allergens, such as bee venom. Tryptase is a marker for the activity of mast cells --one of the two cell types generally considered responsible for triggering the many symptoms associated with allergy. Plaut says that the normal tryptase levels seen here "make you wonder if we understand why these patients die"- if there isn't something other than mast cells at work.

Somewhat to his surprise, Sampson notes that among the cases he reviewed, epinephrine - the primary drug for reversing allergic symptoms - did not prevent severe food reactions. However, he says, it "did buy patients time to reach a medical center." Indeed, no child who received early treatment with epinephrine died.

John W. Yunginger of the Mayo Clinic in Rochester, Minn., sees a major message there: Physicians should prescribe and train families of allergic patients in the use of kits containing epinephrine. Wesley Burks, a food-allergy researcher at Arkansas Children's Hospital in Little Rock, agrees but adds that "it's very atypical for a practicing physician to do that."

Finally, the study's authors note that none of the children knowingly ate foods containing items to which they were allergic. That's not surprising, Yunginger says, since food labels currently mask several problem items. For instance, he notes that "reflavored" peanuts are sometimes labeled "artificial walnuts" because they look and taste like walnuts. Not only is that label "totally uninformative:' he says, "but it also could pose a lethal risk to certain people." Three of the six deaths in this study resulted from allergies to peanuts.

Nor are labels the only problem. Last year, Sampson's team discovered why children with milk allergies occasionally react severely to certain "nondairy" foods: The researchers found namebrand products heavily contaminated with milk protein. -J. Raloff