As many as 13 million Americans suffer from insect venom allergies, though the incidence may be increasing due to the growing number of fire ants. The insects that cause allergic reactions belong to the Hymenoptera order, including bees, wasps, ants and several other species. A normal response to a sting from these insects includes redness and swelling, but it is important to be able to recognize the signs of anaphylaxis. Predicting the severity of subsequent reactions depends upon several factors, including the amount of venom exposure during the sting. Allergic patients should be trained in how to prevent and treat their insect venom allergy.

 
Incidence

It is estimated that 0.5% to 5% of the population of the United States, or as many as 13 million people, have insect venom allergies.^1,2 Many of these venom-sensitive individuals are at risk for life-threatening anaphylactic reactions. An estimated 40 to 100 deaths due to anaphylaxis caused by insect venom are reported each year, half of which are attributed to fire ants, an increasingly common pest that is spreading throughout the United States from the south.^2-5 The total number of deaths from insect stings, however, may be higher.

 
Common Culprits

The insects most commonly associated with triggering severe allergic reactions belong to the Hymenoptera order of insects. This order is comprised of:

• Bees
• Wasps
• Yellow jackets
• Hornets
• Ants, including the fire ant

You may wish to learn more about these stinging insects, including information about their appearance and stinging abilities, what to do if someone is stung, and how to avoid being stung.

 
Normal Response Versus Anaphylaxis

A normal response to an insect sting results in swelling, pain, and redness around the site of the sting or bite. When a person is allergic to an insect sting, he or she is susceptible to the effects of anaphylaxis, which 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
• Rapid fall in blood pressure
• Shock and loss of consciousness

It is important to remember that these symptoms can progress to deadly anaphylaxis in 1 to 2 minutes.⁶

 
Severity of Subsequent Allergic Reactions

In general, people who have experienced an allergic reaction from an insect sting have an approximately 30% to 60% chance of experiencing a similar or worse systemic or anaphylactic episode the next time they are stung.⁷ But a person's chance of experiencing subsequent life-threatening allergic reactions varies, depending on factors such as:

• Age⁸
• Health⁸
• The amount of venom to which the person is exposed when stung⁸
• The severity of the initial reaction⁸

It has been shown, for example, that severe initial reactions increase the likelihood of future anaphylactic responses.

On the other hand, some people who have experienced allergic reactions to insect stings will see the severity of their reactions decrease over time or even cease spontaneously.⁹

 
Protection, Prevention, and Treatment

As with any severe allergy, the primary method of protection is a two-step process:

1. Avoiding contact with allergens
2. Being prepared to treat anaphylactic emergencies by carrying self-injectable epinephrine followed by emergency medical care

Unlike people susceptible to anaphylaxis triggered by food, medications, or latex, people allergic to insect venom have the option of undergoing immunotherapy, a preventive course of treatment that provides long-term protection against insect sting allergies.

Avoidance
Avoidance is a key element in guarding against severe allergic reactions to insect stings. Simple steps that people can take to avoid attracting or provoking stinging insects when outdoors are:

• Avoiding brightly colored clothing or sweet-smelling cosmetics and shampoos
• Keeping food and garbage covered
• Wearing shoes to guard against stepping on insects
• Keeping the arms and legs covered during activities (such as gardening or hiking) that may expose them to stinging insects
• Refraining from swatting or crushing insects
• Steering clear of areas where insects have nested

Immunotherapy
Doctors should discuss the option of venom immunotherapy (VIT) with their patients who suffer from severe allergic reactions to insect stings. During VIT, patients undergo a series of injections that expose them to minute amounts of pure venom. The dosage is slightly increased over the course of the therapy, helping the patient build a tolerance to the venom proteins that triggers allergic reactions. VIT is 97% successful in preventing future allergic reactions in patients allergic to insect stings and is usually completed after 3 to 5 years of regular injections.^10,11

Even after patients have been treated with VIT, however, they may be advised to carry self-injectable epinephrine because not all patients will remain tolerant to insect venom for life.⁸ Moreover, VIT itself poses a 6% risk of anaphylaxis because of the venom used in the therapy. Physicians treating patients with immunotherapy should keep epinephrine and other resuscitation medications and equipment needed to treat anaphylaxis on hand.

You can learn more detailed information about immunotherapy in our treatment guidelines section.

Emergency Treatment
Because not all stings can be avoided, the American Academy of Allergy‚ Asthma‚ and Immunology recommends that people allergic to insect stings be prepared to administer injectable epinephrine to themselves immediately if they are stung.¹² People with insect sting allergies should carry a self-injectable form of epinephrine, such as EpiPen^® or EpiPen^® Jr epinephrine auto-injectors, with them at all times. Epinephrine (adrenaline) works rapidly to reverse the symptoms of anaphylaxis by relaxing smooth-muscle tissue in the lungs, increasing the heart rate, combating urticaria, and reducing the swelling of the mouth, throat, and face.

The side effects of epinephrine may include palpitations, tachycardia , sweating, nausea and vomiting, and respiratory difficulty. Cardiac arrhythmias may follow the administration of epinephrine. Physicians should instruct their patients about the circumstances under which this life-saving medication should be used.

Many physicians also recommend taking antihistamines, such as diphenhydramine, to relieve the symptoms of allergic reactions, but antihistamines are not a substitute for epinephrine. Only epinephrine can stop the potentially deadly effects of anaphylaxis.

Even after epinephrine has been administered, emergency medical treatment should be sought at once because severely allergic people who have experienced anaphylaxis may need emergency respiratory or cardiac care, or even to be resuscitated if they stop breathing altogether. More commonly, these patients will need professional care to determine whether additional epinephrine, steroids, antihistamines, or other treatments are required. Either way, follow-up diagnosis and care by medical professionals after the self-administration of epinephrine for insect stings are critical for recovery.

Delayed or secondary reactions do occur, and patients should remain under medical supervision for at least 4 hours after an episode of anaphylaxis.¹³

Finally, because stinging insects are difficult to avoid completely, patients who have been treated for an anaphylactic reaction should protect themselves against further episodes by requesting a prescription for self-injectable epinephrine from the emergency room physician and carrying it with them at all times, particularly when outdoors. Physicians should also instruct their patients whether antihistamines should be carried in addition to epinephrine. Advising the patient to wear a medical identification bracelet describing their allergies and susceptibility to anaphylaxis can help ensure prompt, proper treatment during an emergency.

 
References

1. Golden BK, Marsh DG, Kagey-Sobotka A, et al. Epidemiology of insect venom hypersensitivity. JAMA. 1989;262:240-244.
    
2. Valentine MD. Anaphylaxis and stinging insect hypersensitivity. JAMA. 1992;268:2830-2833.
    
3. AAAAI. Anaphylaxis in schools and other child-care settings. Position statement #34. J Allergy Clin Immunol. 1998;102:173-176.
    
4. Lieberman P. Preventing fatalities from anaphylaxis: an allergist-immunologist's perspective. Allergy Proc. 1995;3:109-111.
    
5. Wyatt R. Anaphylaxis: how to recognize, treat and prevent potentially fatal attacks. Postgrad Med. 1996;100:87-99.
    
6. The Merck Manual. 16th ed. Merck Research Laboratories. 1992:331.
    
7. Reisman RE. Natural history of insect sting allergy: relationship of severity of symptomatic initial sting anaphylaxis to re-sting reactions. J Allergy Clin Immunol. 1992;30:335-339.
    
8. Graft DF, et al. Position statement on the discontinuation of hymenoptera venom immunotherapy. AAAAI position statement #33. Available at: http://www.aaaai.org.
    
9. Savliwala MN, Reisman RE. Studies of the natural history of stinging-insect allergy: long-term follow-up of patients without immunotherapy. J Allergy Clin Immunol. 1987;80:741-745.
    
10. Joint Task Force on Practice Parameters, American Academy of Allergy, Asthma and Immunology, American College of Allergy, Asthma & Immunology, and the Joint Council of Allergy, Asthma and Immunology. The diagnosis and management of anaphylaxis. J Allergy Clin Immunol. 1998;101(6 pt 2):S465-S528.
     
11. Hunt KJ, Valentine MD, Kagey-Sobotka A, et al. A controlled trial of immunotherapy in insect sting hypersensitivity. N Engl J Med. 1978;299:157-161.
     
12. AAAAI. The use of epinephrine in the treatment of anaphylaxis. Position statement #26. Available at: www.aaaai.org.
     
13. Wood RA. Anaphylaxis in children. Patient Care. 1997;31(13):161.