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One Is Not Enough for Sting Allergy Tests

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May 25, 2001 -- Marianne Frieri, MD, PhD, recalls the day her father almost died from a yellow jacket sting. He was in his early 70s, driving down a country road. When he was stung, he kept on driving, and the person behind him noticed he was weaving. "When he crashed into a tree, the next driver called 911, and they gave him a shot of adrenalin in time to save his life," his daughter says.

Although everyone has had an insect sting, few of us have had a reaction like Frieri's father. Most of us have experienced a local reaction, where the area around the sting gets red, swollen, and painful for a few days. It's easy to treat a local reaction with topical ointments and home remedies.

However, sometimes the entire body reacts to an insect sting, and this systemic reaction -- the kind Frieri's father had -- can be life-threatening. Signs include shortness of breath, chest tightness, hives, flushing, itching, redness, and a drop in blood pressure.

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"People with severe symptoms such as intense itching all over the body or lightheadedness and dizziness should go to an emergency room," says Frieri, director of allergy and immunology at Nassau University Medical Center, in East Meadow, N.Y. Frieri is professor of medicine at SUNY-Stony Brook.

When a person has a bad reaction to an insect sting, doctors use a venom skin test to check for insect sting allergies.

"Some people are allergic to stinging insects such as bees, wasps, yellow jackets, and hornets," says David B.K. Golden, MD. "Venom immunotherapy, or allergy shots, are 99% successful in controlling this allergy. It usually takes two months of shots, plus booster shots every month or two for the next five years." Golden is associate professor of medicine at Johns Hopkins University, in Baltimore.

If the skin test is negative, a person may be told they don't require allergy shots and don't have to worry about another severe reaction. However, a study in the May issue of the Journal of Allergy and Clinical Immunology finds that even if one test is negative, you still may be at risk for a severe reaction.

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In a study, led by Golden, researchers looked at 99 people who had had a systemic reaction to an insect sting but had a negative reaction to the insect venom skin test. They found that in about a third of those people, further blood tests showed positive responses to insect venom.

"This is very interesting research, and supports some of the observations doctors have made over the years," says Leonard Bielory, MD. "While the skin test is the gold standard, it is not perfect. Some people are positive on the skin test, some on the blood test. You should still get a skin test, but consider the blood test as complementary, and get that, too."

Bielory is director of the Asthma and Allergy Research Center of the New Jersey Medical School, in Newark.

The main message is that one test is not enough, Golden says. If someone thinks he may be allergic to insect stings, but a skin test is negative, it's a good idea to get a blood test. If that is negative, wait 6 months and get another skin test.

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"If all three tests are negative, we start to feel more comfortable that you really don't have the allergy," Goldman says, "And we might still give you an emergency injector kit to take home, just in case."

Another safeguard when having an insect allergy test: Be sure to tell the doctor about all drugs you've been taking, even over-the-counter remedies like Benadryl and herbal medicines. These can interfere with the results of the tests, says Frieri, so take an inventory of your medicine cabinet before you head to your doctor's.

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