NEW YORK (Reuters Health) - Scientists have found one way to predict which people may have life-threatening allergic reactions to bee and wasp stings. Elevated levels of a particular enzyme can signal who is at risk, according to a report.

In a study of 114 people with a history of allergic reactions to bee or wasp stings, German researchers found that 12 had elevated blood levels of an enzyme known as tryptase. More importantly, 9 of these 12, or 75%, had suffered severe reactions to stings, compared with only 28% of the rest of the study group.

Dr. Dagmar Ludolph-Hauser of Ludwig-Maximilians-Universitat Munchen, Germany, and colleagues report their findings in the February 3rd issue of The Lancet.

Tryptase is an enzyme that is found in mast cells, which are immune system cells that are central players in allergic reactions. Chronically high concentrations of the enzyme are linked to mastocytosis, a rare condition marked by an accumulation of mast cells in the skin or throughout the body. In this study, the researchers found that almost all of the study participants with raised tryptase levels had mastocytosis of the skin.

Because people with mastocytosis have a high number of mast cells, they appear to be at increased risk of severe reactions to bee and wasp stings, Ludolph-Hauser told Reuters Health.

She noted that about 5% of adults in Europe and the US suffer entire-body reactions to bee and wasp stings, and about one quarter of these individuals have severe, potentially fatal reactions. According to these findings, she said, many patients with severe reactions also have mast cell disease.

These patients, Ludolph-Hauser added, may require life-long treatment with injections of bee or wasp venom, which could prevent the immune system from overreacting to a sting.

SOURCE: The Lancet 2001;357:361-362.