Allergy Clinical Services

Stinging Insect Allergy

Each year, many Americans are stung by bees, wasps, hornets, yellow jackets, and fire ants. These insects, members of the Hymenoptera family, inject venom into their victims when they sting. Some people develop severe allergic reactions when their immune systems react to the venom. An allergic reaction to an insect sting follows this process:

After a first sting, an allergic person's body produces an allergic substance called IgE antibody, which reacts with the insect venom.

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Reactions to stings commonly last only a few hours. Redness and swelling may develop at the site of the sting; pain and itching are also common. Occasionally, these reactions will grow larger and last as long as two weeks. This is called a large local reaction. Depending on its severity, this type of reaction may also require medical treatment.

For a very small number of people allergic to insect venoms, such stings may be life-threatening. Severe allergic reactions to insect stings can involve many organ systems of the body and may develop rapidly after the insect stings. These symptoms can include itching and hives over much of the body, swelling in the throat or tongue, difficulty in breathing, dizziness, severe headache, stomach cramps, nausea, or diarrhea. In severe cases, a rapid fall in blood pressure may result in shock and loss of consciousness. All of these symptoms indicate a type of serious allergic reaction called anaphylaxis. Anaphylaxis is a medical emergency, and may be fatal if the sting victim does not obtain immediate medical treatment.

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Identifying and avoiding stinging insects

To avoid stinging insects, it's important to learn what they look like and where they live. Most stings are from five types of insects: yellow jackets, honeybees, fire ants, paper wasps, and hornets.

Yellow jackets

These insects are black and have yellow markings (see Figure 1). The queens measure about > inch long; the males and workers are about = inch long. These insects are found from arctic to tropical regions, but are less common in the southwestern United States. Yellow jackets' nests are made of a papier-mâché material they produce by chewing up rotted wood, dead stems and leaves, or paper and cardboard. Their nests are usually underground, but can sometimes be found inside the walls of frame buildings, in cracks in masonry or in woodpiles. They become more aggressive over the summer and are commonly found around foods and sweets. They are easily agitated.

Honeybees

Honeybees are about = inch long, and have a rounded hairy body with dark brown coloring and yellow markings (see Figure 2). They have a barbed stinger that they commonly leave in a victim upon stinging. This is an excellent way to identify the stinging insect. After stinging they die; they are fairly nonaggressive and will only sting when provoked. A common setting for a sting is bare feet in a lawn of clover. However, Africanized honeybees, or so-called "killer bees," which are found in the southwestern United States and South and Central America, are more aggressive and may sting in swarms.

Domesticated honeybees live in man-made hives, while feral honeybees live in colonies, building nests in hollow trees or in the cavities of buildings. Hives are constructed of beeswax and consist of repeating parallel vertical combs, or "honeycomb." Africanized honeybees are less selective about nesting sites. Common sites include holes in exteriors of homes, between fence posts, in old tires or holes in the ground, or any other partially protected site.

Paper wasps

These insects' slender, elongated bodies are = inch to one inch long and are black, brown, or red, usually with yellow markings (see Figure 3). Their nests are also made of a paper-like material that they produce, and are composed of a circular comb of cells that open downward. The nests are often located under eaves, behind shutters, or in shrubs or woodpiles.

Hornets

Hornets are black or brown with white, orange or yellow markings and are usually larger than yellow jackets, typically > to one inch long (see Figure 4). Their nests are gray or brown and football shaped, and are made of a paper material similar to that of yellow jackets' nests. Hornets' nests are usually found high above ground on branches of trees, in shrubbery, or on gables; one type nests in tree hollows.

Fire ants

These are reddish brown and approximately 1/8 inch in length (see Figure 5). They build their colonies in the ground, with prominent mounds (see Figure 6). These fire ant beds are often found along the borders of sidewalks, driveways and along roadsides. Eliminating these colonies is difficult, since most of the nest is underground, and numerous colonies can be found in the area. Fire ants are typically found in Southern states (South Carolina to Florida and Texas).

Stay out of the "territory" of the stinging insects' nests to avoid encountering large numbers of them. Since all of these social insects will sting if their homes are disturbed, it is important to destroy hives and nests around your home. The insect-allergic person should not perform or be near this potentially dangerous activity. A trained exterminator should be employed.

Inspect the home and yard weekly, especially in spring and summer, to detect new hives or nests. Paper wasp nests may be eliminated spraying with a contact insecticide on a cool night. Fire ant nests are best treated with approved baits, but can also be treated with an approved drench insecticide. Individuals treating nests should wear appropriate protective clothing.

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Preventing stings

Remain calm and quiet when you encounter any flying stinging insects and move slowly without flailing your arms. Since the smell of food attracts insects, be careful when cooking, eating, or drinking sweet drinks like soda or juice outdoors. Keep food covered until eaten, especially soda and juice cans. Insects are attracted to trash containers; keep these areas clean, cover garbage, and use natural insecticide sprays. They also like bright colors and fragrances.

Because honeybees gather nectar from clover and other ground plants, wear closed-toe shoes outdoors and avoid going barefoot. Swimming pools and flower gardens are particularly high-risk areas. Avoid loose-fitting garments that can trap insects between material and skin.

Gardeners should take additional precautions. Accidentally disturbing a nest will irritate the insects, inciting them to sting. Watch out for nests in trees, shrubs, woodpiles, under the eaves of the house, and in other protected places. Use hedge clippers, power mowers, and tractors with caution.

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Treating stings

Severely insect-allergic people should not participate in outdoor activities alone, because if they are stung, they may require assistance in receiving prompt emergency treatment.

Among Hymenoptera species, the honeybee commonly leaves a stinger (with venom sac attached) in the skin of its victim. Since it takes several minutes for the venom sac to inject all of the venom, immediate removal of the stinger and sac (within 30 seconds) will limit the amount of venom injected. A quick scrape of the fingernail removes the stinger and sac. Avoid squeezing the sac since this forces more venom through the stinger and into the skin. Hornets, wasps, and yellow jackets do not usually leave their stingers in their victims. These insects should be brushed from the victim's skin promptly with deliberate movements to prevent additional stings. The person should then quietly and immediately leave the area. Fire ants should also be carefully brushed off to prevent repeated stings.

If you/your child begin experiencing any of the serious allergic symptoms described previously, have someone take you/your child to an emergency room immediately. Insect sting reactions can be serious and require immediate medical treatment.

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If you/your child have had reactions before, you/your child should carry an "on the spot" short-term treatment for severe allergic reactions: a self-injectable epinephrine shot. The single- or double-dose syringe is pre-filled with epinephrine, which reduces allergic reactions. Use the injector according to the instructions, and carry it with you/your child whenever you/your child will be outdoors during insect season. Replace the device before the labeled expiration. You/your child should become proficient in self-administering epinephrine in the event that you/your child are stung while alone and develop a sudden anaphylactic reaction. Remember that injectable epinephrine is emergency, rescue medication only. If you/your child use the epinephrine injection, you/your child must still have someone take you/your child to an emergency room immediately. Additional medical treatments may be necessary for the management of some insect sting reactions.

Immunotherapy

We will recommend testing to determine whether the person has an allergy and which type of stinging insect caused the reaction after a careful history. Skin or blood (RAST) testing for insect allergy is used to detect the presence of significant amounts of IgE antibody in the patient.

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Those who are severely allergic to the venom of stinging insects should receive venom immunotherapy, a highly effective vaccination program that actually prevents future allergic sting reactions in 97 percent of treated patients. It is the closest thing to a "cure" and is highly recommended. The indication should be discussed carefully with the Allergist. Children and adults are treated differently.

During immunotherapy, the doses of venom extract gradually increases every few weeks over a period of three to five years. This helps the patient's immune system to become more and more resistant to future insect stings.

Those who have severe allergies may also want to wear a special identification tag in the form of a bracelet or necklace that identifies the wearer as having severe insect sting allergy. These tags can also supply other important information about the patient's medical condition.

Adapted from American Academy of Allergy Asthma and Immunology's Tips to Remember.

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Reviewed by: Allergy Section
Date: April 2004

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