Insect Sting Allergies

Stinging insects found in the United States include honeybees, yellow jackets, hornets, wasps, and fire ants. While not everyone is allergic to insect venom, reactions in the skin such as mild pain, swelling, and redness may occur with an insect sting.

Nonallergic reactions

Most insect-sting reactions are not allergic and result in local pain, itching, swelling, and redness at the site of the sting. Some extension of the swelling is expected. Local treatment is usually all that is needed for this type of reaction. Disinfect the area, keep it clean, and apply ice. Topical corticosteroid creams are sometimes used to decrease inflammation, and antihistamines can help control itching.

Large local reactions may involve increased swelling (that lasts for 48 hours up to one week) that may be accompanied by nausea and vomiting. Large local reactions occur in about 10% of insect stings and are not allergic in origin. Occasionally, the site of an insect sting will become infected, and antibiotics are needed.

Allergic reactions

Systemic (body-wide) reactions are allergic responses and occur in people who have developed antibodies against the insect venom from prior exposure. It is estimated that between 0.3%-3% of stings trigger a systemic allergic reaction.

Over 2 million Americans are allergic to stinging insects. The degree of allergy varies widely. Most people are not allergic to insect stings, and most insect stings result in only local itching and swelling. Many, however, will have severe allergic reactions. Severe allergic reactions to insect stings are responsible for at least 50 deaths each year in the U.S.

If you are known to be allergic to insect stings, then the next sting is more likely to be similar to or worse than the previous sting. Since most stings occur in the summer and fall, you are at greatest risk during these months. Males under the age of 20 are the most common victims of serious insect-sting allergic reactions, but this may reflect a greater exposure to insects in males, rather than a true predisposition.

The allergic reaction to an insect sting varies from person to person. Symptoms of an allergic reaction can include itching, hives, flushing of the skin, tingling or itching inside the mouth, and nausea or vomiting.

The most serious allergic reaction is called anaphylaxis, which can be fatal. Difficulty breathing, swallowing, hoarseness, swelling of the tongue, dizziness, and fainting are signs of a severe allergic reaction. These types of reactions usually occur within minutes of the sting but have been known to be delayed for up to 24 hours.

Prompt treatment is essential, and emergency help is often needed.

Allergy specialists and immunologists are physicians specialized in diagnosing allergies and prescribing allergy injection therapy for stinging-insect allergies (see below). The actual allergic reaction itself may be treated by emergency medicine or primary-care physicians, including pediatricians, internists, or family practitioners.

In a person with a known insect sting allergy, the presence of the signs and symptoms of an allergic reaction following a sting or bite is typically sufficient to establish the diagnosis of an allergic reaction.

A person who is unsure whether or not they have an allergy to stinging insects can consult an allergist/immunologist physician for testing. Two types of tests, skin tests, and blood tests can be used to determine whether or not you have an allergy to specific types of stinging insects. Skin testing involves placing a sample of the insect venom on or slightly under the top level of the skin and observing the area for signs of an allergic reaction. Blood testing involves a test called a radioallergosorbent test (RAST) to determine the amount of IgE antibodies in your blood to a specific substance.

Honeybee stingers are barbed stingers that are left behind in the person's skin after the initial sting. If the stinger is removed by pinching the stinger, more venom is injected into the skin. It is better to remove the stinger by gently lifting the stinger using a fingernail or knife edge to flick the stinger out of the skin. Other stinging insects do not leave stingers behind and this technique does not apply.

An allergic reaction is treated with epinephrine (adrenaline). Several self-injectable devices are available by prescription, including EpiPen, Auvi-Q, and others. These devices are filled with epinephrine to be injected into the subcutaneous tissue or muscle, preferably into the front of the thigh. These self-injected devices usually contain only one dose and, on occasion, more than one dose is needed. Venom extractors are commercially available, but they have not been demonstrated to have any benefit.

If a serious sting reaction occurs, always seek medical attention, even if epinephrine is used and all seems stable. The allergic reaction can subsequently progress and become more serious after epinephrine has worn off. Sometimes epinephrine is not enough and intravenous fluids or other treatment is needed. If you are known to be seriously allergic to insects, you must remember to carry the epinephrine at all times especially when out of reach of medical care (such as in the woods or even on an airplane). If epinephrine is not available when you are stung, contact a doctor as soon as possible. In addition to epinephrine, an oral dose of an antihistamine (like diphenhydramine [Benadryl]) can reduce the symptoms of an allergic reaction. Antihistamines take effect in about one hour. Ultimately, however, it is crucial to attempt to avoid the sting.

There are no home remedies that can prevent an allergic reaction or treat a severe reaction such as anaphylaxis.

You can take steps to relieve the symptoms of a mild allergic reaction, including:

• Taking an oral antihistamine such as diphenhydramine (Benadryl) or using a topical steroid cream
• Applying cold compresses to the affected area
• Cleaning the area with soap and water to prevent secondary infection

All people who have had a significant reaction to a stinging insect should be evaluated by an allergy specialist for possible venom immunotherapy (allergy shots that develop an immunity to insect allergy). Selected patients with significant sensitivity to insect venom and specific symptoms can undergo allergy injection therapy for stinging-insect allergy. Allergy immunotherapy against stinging insects in these selected patients is almost 100% effective.

This type of treatment usually involves a gradually increasing dose of the venom over 10-20 weeks. Then a "maintenance" dosage every four to eight weeks is given. After approximately three to five years, discontinuation of the venom shot is considered. Therapy for three to five years confers long-term protection in most people. The risk of severe adverse reactions from this venom therapy is minimal (less than 0.2%), and no deaths have been reported to date.

The U.S. Department of Agriculture recommends the following:

• Avoid disturbing likely beehive sites, such as large trees, tree stumps, logs, and large rocks.
• If a colony is disturbed, run and find cover as soon as possible. Running in a zigzag pattern may be helpful.
• Never stand still or crawl into a hole or other space with no way out.
• Do not slap at the bees.
• Cover as much of the head and face as possible, without obscuring vision, while running.
• Once clear of the bees, remove stingers and seek medical care if necessary, especially if there is a history of allergy to bee venom.

Most people recover from allergic reactions to insect stings without further complications. Those who have a history of severe reactions or anaphylaxis should always carry a self-injecting epinephrine source. Immunotherapy (allergy shots) for insect sting allergy as a treatment choice has an excellent outcome for certain people with insect sting allergy.

The best treatment is avoiding the insect sting. Certain precautionary measures will greatly decrease your chances of being stung. Honeybees are not aggressive and will usually not sting unless disturbed or injured. The majority of honeybee stings are on the bottom of the bare foot while stepping on the bee. Avoid walking barefoot on lawns where honeybees or other stinging insects may be present. Yellow jackets nest in the ground and walls. Caution should be used with unusual forms in walls and mounds in the ground. Hornets and wasps often nest in bushes, in trees, and under roofs. Use caution too in these areas and in selecting employment requiring exposure to these conditions.

Bright colors attract insects seeking nectar. Stinging insects are attracted to food and strong smells. Avoid open food in garbage cans, dumps, and open picnic areas. Do not wear perfumes, hair sprays, and colognes. Keep the body covered as much as possible with light-colored clothing. Insect repellents are not effective against stinging insects.