by Duane Wong, M.D.
Insect sting allergy is a significant medical problem and occurs with increased frequency in children. It is responsible for approximately fifty deaths per year in the United States.
The major winged stinging insects belong to the order Hymenoptera of the class Insecta and include the honeybee, wasp, yellow jacket, and hornet. Honeybees belong to the superfamily Apoidea. They generally travel in a direct line between destinations, and stings generally occur when someone interrupts a bee in flight or disturbs a flower where a bee has landed. Multiple stings generally occur only when a hive is endangered. Wasps, yellow jackets, and hornets belong to the superfamily Vespoidea. Vespids feed on a variety of foodstuffs, particularly juices, saps, and nectar. They are attracted by odors such as soft drinks, perspiration, and spoiling foods.
Clinical manifestations can include the following:
Local reactions. The expected reactions after an insect sting consist of pain, swelling, and redness at the sting site, which resolve in several hours. These reactions may peak at 24 to 48 hours and last for up to one week.
Unusual reactions. These may affect the nervous system, the kidneys, joints, and blood vessels.
Anaphylactic (severe allergic) reactions. The usual reaction includes generalized hives, swelling, and flushing. More serious symptoms may include breathing and blood pressure changes. In general, the symptoms begin within a few minutes after the insect sting, but in rare instances, may start as late as several hours after the sting. There may be no warning of the development of insect sting anaphylaxis as it may occur after the first sting exposure. Although most allergic reactions to stinging insects occur in individuals less than 20 years of age, the great majority of deaths from sting anaphylaxis occur in adults over 40 years of age.
Toxic reactions. These occur as a result of multiple stings. Insect venom contains a number of chemicals which can cause symptoms that may mimic those seen in anaphylaxis.
Individuals who have had a suspected generalized reaction to a stinging insect may be skin tested with five available purified venom extracts (honeybee, yellow jacket, bald-faced hornet, white-faced hornet, and wasp). Patients with only a family history of insect sting allergy but who have not yet been stung, should not be skin tested with venom extracts. While blood tests have also been used to diagnose insect sting allergy, skin testing continues to be considered the “gold standard” for diagnosis.
Therapy for insect sting allergy includes avoidance measures to reduce exposure to stinging insects, emergency medications for treatment of anaphylaxis, and specific venom immunotherapy – allergy shots.
Avoidance. Individuals at risk should always wear protective clothing when in grass or fields and should wear gloves when gardening. Bright colored clothing should also be avoided as it tends to attract insects. As food and odors attract insects, garbage should be well wrapped and covered. Colognes, hair spray, and fragrant cosmetic use should be minimized. Insect repellents have not been demonstrated to be effective in reducing the frequency of insect stings.
Local reactions. Treatments should begin with cold compresses, oral antihistamines, and analgesics. Oral corticosteroids may be helpful in reducing the swelling associated with especially large and painful reactions.
Anaphylaxis. Acute allergic reactions caused by insect stings can be a medical emergency and victims should be seen by a physician, on an emergency basis, as soon as possible. Patients at risk for anaphylaxis should be instructed to self-administer epinephrine. Kits such as the Ana-Kit (Hollister-Stier Laboratories) or Epi-Pen (Center Laboratories) can be lifesaving in instances when immediate medical attention is not available. Moreover, medical alert bracelets can help insure appropriate medical treatment in case consciousness is lost. While intensive care therapy may be required in cases of severe reactions, most will subside within a matter of minutes or hours, even without therapy.
Venom immunotherapy (allergy shots). This has been shown to provide protection for over 95% of patients with a previous history of anaphylaxis following an insect sting. Venom immunotherapy should definitely be administered in adults and children who have had a sting reaction with breathing or blood pressure problems. Because of the higher risk of death following anaphylaxis in adults, adults with only generalized hives should also undergo venom immunotherapy. Children with hives alone, however, do not require venom immunotherapy. Venom immunotherapy is not given to patients with only local, unusual, or even toxic reactions.
Posted in: Insects