Patient Education

STINGING INSECT ALLERGY

Copyright 2000, Regional Allergy & Asthma Consultants, PA

INTRODUCTION:

Approximately 1 in 100 people has a potentially life-threatening allergy to insect stings. The insects most often responsible for serious allergic reactions are honey bees, wasps, hornets, yellow jackets, and fire ants. Mosquitoes, fleas, and other biting insects do not usually cause serious allergic reactions. Although intimidating by virtue of size, bumblebees rarely sting.

A severe allergic reaction can involve the whole body and advance very rapidly after the sting.  Itching, hives, or swelling may appear at sites distant from the actual sting site.  Difficulty in breathing, wheezing, feeling tight in the throat or difficulty swallowing may occur.  Dizziness, nausea, vomiting,  a drop in blood pressure, shock, and unconsciousness may also occur.  Such severe reactions may prove fatal if medical treatment is not obtained immediately.  Approximately 50 to 100 people in the United States die each year from a sting reaction. 

Once an individual has experienced a severe reaction, he or she has a 50-60% chance of experiencing a similar or more severe reaction with each future sting. Therefore, anyone who has experienced any of the above symptoms following a sting should be evaluated by an allergist for allergy testing and consideration for desensitization to venom, in order to minimize the likelihood of future reactions

A reaction to an insect sting that is confined to the actual sting site, regardless of how large or uncomfortable the reaction or swelling may become (e.g. a sting to a finger leading to swelling of the entire arm), is not considered a serious or life-threatening allergic problem.  This type of local reaction may need medical treatment at the time, but not allergy evaluation unless associated with other symptoms distant from the sting site.

WHO GETS INSECT STING ALLERGIES?

People of any age may develop an allergy to insect stings.  It is not usually inherited, and is just as common in patients without any previous history of allergies as it is in people with hayfever, asthma, or eczema.  Generally, severe sting reactions occur following previous stings to which there was no reaction. Occasionally, a life-threatening reaction may develop following a person's first sting.

HOW IS INSECT STING ALLERGY DIAGNOSED?

Skin testing is performed using dilute solutions of the actual venoms of stinging insects.  Since there is much similarity and cross-reactivity between some of the venoms, and because many patients cannot be absolutely certain of the species of insect that caused the reactions, we generally test to all of the relevant venoms.

WHO SHOULD BE TESTED FOR INSECT STING ALLERGIES?

Anyone who has experienced a reaction distant from the site of a sting should be tested. This includes itching, hives, swelling, breathing problems, dizziness from low blood pressure, fainting, nausea or shock. For unclear reasons, children who develop hives from insect stings are not at risk for developing more severe reactions with future stings, and allergy testing and desensitization are not routinely recommended.

Patients who have experienced only local reactions to stings, even if quite large, generally do not need testing.

HOW IS INSECT STING ALLERGY TREATED?

Patients who have experienced a serious insect sting reaction and who have a positive skin test to any of the venoms should be treated with a series of desensitization injections. This will reduce the likelihood of another severe reaction from about 50 percent in the untreated state to less than 1 or 2 percent with future stings. Injections are given approximately weekly until a maintenance dose is reached, usually in about 4 months. At that point, tolerance to the venoms has developed, and the injection schedule can gradually be changed to every 4 weeks and later to every 6 weeks. The total length of treatment varies depending on several factors, including the severity of the initial reaction, the degree of sensitivity, the likelihood for future stings, immediate access to medical care, etc. A minimum of 4 years is recommended, although some individuals will require lifelong treatment.

All patients with stinging insect allergy should have a pre-filled syringe of epinephrine immediately available when they are at risk for sustaining insect stings. This is available either as a single dose auto-injector (Epipen) or a manually injectable syringe containing two doses (Ana-Kit). Epinephrine should be administered immediately with the onset of any life-threatening signs or symptoms (tightness in the throat or chest, difficulty breathing, dizziness, loss of consciousness) and should be followed by transport to the nearest emergency room for additional care. Keep in mind that epinephrine, although very effective, is also very short-lived (15-20 minutes), and many anaphylactic reactions will redevelop after epinephrine wears off. The use of this medication is therefore considered a temporizing measure, not a substitute, for seeking medical care. An antihistamine, such as Benadryl, should also be used, but only after epinephrine has been administered.

Finally, some general avoidance measures should be undertaken by those with stinging insect allergies:
1. Avoid perfumes and scented lotions, which may attract insects.
2. Wear shoes outdoors at all times.
3. While dining outdoors, keep food covered until eaten, and leave clean-up to others.
4. Yard work, gardening and landscaping should be done with extreme caution, or better yet, delegated to a non-allergic family member, friend, or lawn company.
5. During warm weather seasons, the area around the home should be periodically inspected by a non-allergic relative, friend, or professional pest control company.
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