Curbing allergy to insect venom: therapy stops reactions to stings years later.

Immunizing adults against insect-sting allergies has proved highly effective since it was first tested in the 1970s. But while many children receive shots for allergies such as hay fever, they're much less likely than adults to receive allergy shots against insect venom--in part because many parents and doctors believe that children typically outgrow this kind of allergy, says David B.K. Golden of Johns Hopkins Medical Institutions in Baltimore.

A new study of people with an insect-sting allergy shows that those who received allergy shots as children still benefit from them as young adults. Moreover, the study suggests that while most children do indeed outgrow sting allergies, many don't. These children remain at risk of having severe reactions later in life, Golden and his colleagues report in the Aug. 12 New England Journal of Medicine.

The study"sends a clear message," comments John E. Moffitt of the University of Mississippi Medical Center in Jackson. "Children who have a moderate-to-severe reaction to insect stings [and who] test positive for allergy would be candidates for allergy shots."

In addition to the pain they inflict, insect stings can cause a localized allergic reaction on the skin. More serious is a systemic allergic reaction, in which rashes or hives pop up on skin away from the sting site.

The worst systemic reactions are called anaphylaxis and are marked by difficulty in breathing, throat swelling, dizziness, nausea, plummeting blood pressure, or unconsciousness. At least 40 people die every year in the United States from severe anaphylactic reactions triggered by the stings of yellow jackets, wasps, bees, hornets, or fire ants.

Golden and his colleagues tracked down 512 people who, as children, had visited a doctor between 1978 and 1985 because they had a reaction to an insect sting. Follow-up interviews revealed that nearly half of the participants had been stung again between 1987 and 1999. On average, the children had been 8 years old at the time of their previous stings and 21 when they were stung again.

During the intervening years, some of the study participants had received a series of sting-allergy shots. The treatment provides purified insect venom that dampens subsequent reactions to stings. Researchers found that only 3 percent of those who had received the allergy shots experienced any systemic allergic reaction from the later sting, compared with 17 percent of people who hadn't gotten the shots.

When the researchers focused on participants who had had an anaphylactic reaction to a sting as children, they found that a later sting induced a similar reaction in only 2 of 43 people who had received the allergy shots but in 7 of 22 people who hadn't.

In addition to showing the effectiveness of the allergy shots, the results demonstrate that a large number of young people allergic to stings but unimmunized remain at substantial risk of a severe reaction, Moffitt says.

Sting-allergy shots protect 95 to 98 percent of adults receiving them, but their effect can wane, necessitating booster shots. The new results hint that sting-allergy shots given during childhood impart longer-lasting protection, Golden says.