Allergy Facts from the Asthma and Allergy Foundation of America

Insect Sting Allergy and Venom Immunotherapy

Many people look forward to summer, which brings the promise of pleasures like long days in the sun, picnics, beaches and baseball. Warm weather, however, also brings some not-so-welcome visitors in the form of stinging insects. For most people, these small creatures are an annoyance that threaten to ruin outdoor fun. But for some 2 million Americans, these insects pose a far more serious threat of a life-threatening allergic reaction.

What Kind of Insects Pose a Threat?

Most insect stings in the United States are caused by Hymenoptera—bees, wasps, hornets, yellow-jackets, and in the Southeast, fire ants. Nature has given these insects a toxic substance called venom, which is a powerful defense against their enemies. In humans, insect venom acts on the circulatory system, causing the blood vessels to dilate, or become wider. This effect ensures that the toxin will be carried quickly throughout the bloodstream. The venom also can disrupt blood cells and nerve cells and, in some persons, can trigger a powerful immune response.

What Are the Signs of a Reaction to Insect Venom?

The response triggered by an insect sting can range from relatively mild, local symptoms to a severe allergic reaction. Most people have a local reaction to insect stings, consisting of redness, swelling, and pain or itching in the area around the sting. These symptoms usually resolve without further problems within hours or days. In some people, however, a sting triggers an allergic reaction, with severe swelling over a large area of the body.

The first time an allergic reaction occurs, the person becomes "sensitized" to the insect venom. The next time the person is stung, he or she may develop anaphylaxis. This is a systemic reaction—one that affects the entire body—and is a potentially life-threatening condition.
Anaphylaxis produces signs and symptoms that require immediate medical attention and that may include:

• Hives, itching and swelling over large areas of the body
• Tightness in the chest and trouble breathing
• Swelling of the tongue
• Dizziness or passing out
• Sharp drop in blood pressure
• Cardiac arrest (heart attack)

How Is a Reaction Treated?

An anaphylactic reaction requires treatment with epinephrine (adrenaline). This is a naturally occurring hormone that helps to ease the effects of the allergic response. The sting victim may also require intravenous fluids and oxygen to assist in breathing.

If you have a large local reaction to an insect sting—such as extreme swelling that takes days or weeks to subside—you may be at risk for anaphylaxis if you are stung again. You should seek medical attention for the reaction from an allergist, who can assess your risk with future stings. The doctor may advise you to carry a kit so that, in the event of a sting, you can inject yourself with epinephrine. You will be taught how and when to use the kit and how to give yourself an injection. If you are squeamish about giving yourself a shot, you may be given a special type of injector that works by simply tapping it against your thigh. It's also a good idea to teach a family member or spouse how to give the injection in case you are unable to do so yourself.

If your doctor finds that you are at risk of experiencing a severe allergic reaction or anaphylaxis after an insect sting, you may be advised to have immunotherapy. This is a series of vaccinations given in the doctor's office at regular intervals. These shots contain very small amounts of insect venom and over time will desensitize your immune system. Venom immunotherapy is highly effective—up to 97 percent of people who complete the series of shots have a significantly lower risk of a severe reaction to an insect sting.

How Can I Protect Myself?

You can't prevent insect stings with bug spray, but there are some common-sense precautions you can take to lower your chances of getting stung.

• The stinging insects love bright colors and sweet smells, so avoid wearing intense colors or perfumes when outdoors.
• Don't leave food out in the open if you are camping or picnicking, and keep trash areas neat and tidy.
• Always wear shoes outdoors to protect yourself in case you step on a bee or wasp.
• If someone near you gets stung, move away from them as quickly as possible—bees and yellow jackets give off a chemical after they sting that arouses other stinging insects that may be in the area. If you are stung, alert others that you may be at risk for a life-threatening reaction.
• Use your epinephrine if you have it, and call 911 right away. Honeybees have a barbed stinger that is left behind in the skin. Do not attempt to remove the stinger by pulling it out—this can actually squeeze more of the venom into the sting site. Instead, work out the stinger by teasing or scraping.

As in most health matters, arming yourself with knowledge and taking steps to prevent problems before they occur are the best ways to protect yourself against insect stings. Working together with your doctor and taking necessary precautions will go a long way toward enhancing your enjoyment of warm and sunny days.

This information should not substitute for seeking responsible, professional medical care.

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