Scientists take buzz out of some bee folklore

Allergic reactions to stings of yellowjackets studied

August 11, 2006|By FRANK D. ROYLANCE | FRANK D. ROYLANCE,SUN REPORTER

It's yellowjacket season.

With their numbers rising and normal foods in short supply, the brassy bugs are crashing our picnics. They compete for our soda, beer, meat and ice cream, and they can deliver painful stings to the unwary. Sometimes they trigger severe allergic reactions.

Scientists who study those reactions - by prodding the insects to sting volunteers - say they have encountered a lot of folklore about yellowjacket stings. And much of it turns out to be flat wrong.

FOR THE RECORD - An article in Friday's Sun about research on yellowjacket stings incorrectly identified the scientific journal in which the study appeared. It was the Journal of Allergy and Clinical Immunology.
The Sun regrets the errors.

For example, many people insist that a yellowjacket's venom gets stronger as summer turns to fall.

"Not true," said Dr. David B.K. Golden, an associate professor of medicine at the Johns Hopkins University, and practicing specialist in allergy and immunology.

There's also a common belief that you can "outgrow" a yellowjacket allergy, and your reaction to the next sting will be milder.

Again, "Our research says it's not true," Golden said.

As it turns out, most American sting victims are likely to be picked on by one of two nearly indistinguishable species of yellowjackets, with drastically different reactions, according to Golden and University of Maryland entomologist Nancy Breisch.

Their work, published in January in the Journal of Allergy and Clinical Entomology, was funded by the National Institutes of Health.

Golden and Breisch have been studying yellowjacket allergies for nine years.

"The vast majority of stings involve sharp initial burning pain, followed by reddening of the skin in a 3- to 4-inch circle and slight swelling at the center," Breisch wrote in an e-mail. "Within a day you have only bad memories and itching."

But a minority of sting victims are allergic. They can have manageable reactions limited to tissues close to the sting, or potentially dangerous systemic reactions that include difficulty breathing, hives, abdominal cramps and loss of consciousness.

The study found that the severity of an allergic reaction most likely depends on how severely the person has reacted in the past, and which species attacks them.

"One sting without a reaction doesn't guarantee you're safe forever," Golden warned. "If you've had a potentially dangerous reaction [in the past], you really should see an allergist and discuss immunization."

That means allergy shots.

For their published study, Golden and Breisch rounded up 111 adult volunteers - all of whom tested positive for yellowjacket allergies.

Breisch then collected yellowjackets of two species - Vespula maculifrons and Vespula germanica. Both are yellow and black, and only experts can reliably tell them apart, she said.

V. maculifrons - the Eastern yellowjacket - is a native of the territory, one of at least a dozen species in Maryland. It lives in underground nests or cavities close to the ground and preys on many insect pests. It tends to sting repeatedly and produces the strongest allergic reactions in the largest percentage of victims.

V. germanica - the German wasp - is a European import. Nesting in the ground or in natural or manmade cracks and crevices, it practices a hit-and-run attack strategy.

Victims also react less severely to V. germanica venom - a difference that wasn't known until this study.

To induce stings, Golden and his team inserted the insects, one at a time, into a modified syringe Breisch devised. It had a wire mesh opening that safely delivered the bug to the volunteer's skin. The plunger then prodded it just enough to make it sting.

It was risky business, Golden said. Some people have only a local allergic reaction - perhaps a badly swollen arm or leg.

"It's only dangerous if it stings your tongue or throat," he said.

But others experience severe reactions - swelling or hives far from the sting site, airway constriction, plunging blood pressure and shock. "It can be quite dangerous," he said.

"We have had some really serious reactions" during the research, he added. That's why all the tests, technically known as "sting challenges," are conducted in a hospital intensive care environment - with intravenous medications, oxygen and expert care on hand, just in case.

Everyone survived the study - except the yellowjackets, which were euthanized.

Golden's goal is to learn what makes people react differently to the same venom.

"We're getting closer, we believe, to being able to predict who is in danger, and who isn't," he said. That will tell doctors who should receive allergy immunization, which is almost 100 percent effective, and who can safely skip the shots.

"Challenge tests are ultimately the best way to see if there is a reaction, and what kind," Golden said.

Why would anyone volunteer to be stung by a yellowjacket?

Golden said some people volunteer because they suspect a prior allergic reaction was a fluke. "They want to know what's going to happen the next time, to help them decide whether they should be immunized," he said.

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