Allergies to Insect Stings

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What are allergies to insect stings?

When you are stung by an insect, poisons and other toxins in the insect's venom enter your skin. It is normal to have some swelling, redness, pain, and itching at the site of a sting. An allergic reaction to the sting occurs when your body's immune system overreacts to substances called allergens that are in the venom of stinging insects.

You may not always develop an allergic reaction the first time you are stung. Even if your first reaction to a sting is mild, allergic reactions can get worse with each sting. Your next reactions may become more severe or even life-threatening.

What causes an allergic reaction to insect stings?

An allergic reaction to an insect sting is caused by sensitivity to allergens in the venom of the insect. Your immune system overreacts to these allergens as though they are harmful, foreign substances in your body.

A few types of stinging insects—such as bees, wasps, hornets, yellow jackets, and fire ants—cause most allergic reactions to insect stings.

What are the symptoms?

Symptoms of an allergic reaction can range from mild to severe. Reddening or swelling around the site of a bite is a normal reaction to the insect venom. Minor, localized allergic reactions cause redness, swelling, fatigue, mild tenderness, nausea, itching, and a low fever, but they do not usually require treatment with epinephrine. Mild reactions are not usually an indication that you need allergy shots (immune therapy) to prevent a worse reaction should you be stung again.

A more serious allergic reaction can spread throughout your entire body (systemic reaction) and cause symptoms such as itching, hives, or swelling of the tongue, throat, or other body parts. A life-threatening allergic reaction called anaphylaxis can cause severe symptoms such as confusion, difficulty breathing, shock, and sometimes death.

How are allergies to insect stings diagnosed?

An allergic reaction to an insect sting is diagnosed by a physical exam and a medical history. Once you have recovered from the allergic reaction, you may be given allergy tests to find which types of insect stings you are allergic to and how sensitive you are to the allergens.

How are they treated?

Treatment for insect sting allergies depends on the severity of your reaction. Mild local and systemic reactions can often be treated with cold packs and medications for pain, swelling, and itching. A severe reaction (anaphylaxis) is potentially life-threatening and requires emergency care.

Avoiding future insect stings can prevent allergic reactions. If you have severe allergic reactions, you should carry an allergy kit, which includes antihistamine tablets and an epinephrine injection. You may also want to seek treatment with a series of allergy shots (immunotherapy) to reduce or eliminate your sensitivity to the insect venom.

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Symptoms of an allergic reaction to insect stings vary from mild to life-threatening. The severity of your allergic reaction depends on your sensitivity to the allergens in the venom—not necessarily on the number of stings or how often you have been stung in the past.

Normal reaction to insect stings

It is normal to have some immediate swelling, redness, pain, and itching at the site of an insect sting—poisons and other toxins in the insect's venom enter the skin when you are stung. Normal symptoms from insect stings may last from a few hours to a few days, don't spread beyond the area of the bite, and include:

• Pain.
• Redness.
• Swelling at the site of the sting.
• Itching at the site of the sting.

Your normal reaction to fire ant stings will be slightly different. Fire ants sting numerous times in a cluster or ring, usually on a person's feet and legs since these limbs are closest to the ground. The stings cause pain, redness, itching, and swelling at the site of the stings. Also, within several hours of being stung, small clear blisters develop at the site and fill with fluid within 24 hours.¹

Large local allergic reactions

A large local reaction is when redness and swelling from an allergic reaction spread outward from the site of the sting. The reaction may affect only the area around the sting itself (such as your hand or forearm), or it may involve an entire limb or a broad area of the body. A large local reaction does not affect the entire body. It often will spread to cross the major joints on either side of the sting, such as the elbow and shoulder if stung on the upper arm. You may also experience a low fever, nausea, or fatigue. Symptoms usually occur within 12 to 24 hours after you are stung, peak within 48 hours, and subside within 5 to 10 days.^{2, 1}

People who have large local reactions to stings sometimes have a more severe local reaction each time they are stung. But for both children and adults, the risk of having a systemic (whole-body) reaction is relatively low, from 1% to 10%.²

Systemic reactions

Symptoms of a systemic allergic reaction develop in a different location than where you were stung and range from moderate to life-threatening. A severe systemic reaction is called anaphylaxis and requires immediate medical treatment.

Common systemic allergic reaction symptoms include:²

• Red, warm skin (flushing).
• Itching.
• Hives.
• Swelling in the deep layers of the skin (angioedema) or mucous membranes (such as the nose and throat). The swelling may occur in the lips, tongue, mouth, throat, ears, eyelids, palms, or soles of the feet.

Serious, life-threatening systemic allergic reaction (anaphylaxis) symptoms can include the symptoms above, as well as:¹

• Swelling and tightness in the throat or chest.
• Wheezing, coughing, and constriction or swelling in the throat that makes it difficult to breathe.
• Dizziness.
• Confusion, agitation, lightheadedness.
• Abdominal cramps, nausea, vomiting, or diarrhea.
• Abnormal heartbeat (arrhythmia).
• A drop in blood pressure.
• Shock that can lead to death.

Systemic reactions usually develop within 15 to 30 minutes or, occasionally, up to an hour after being stung. In some cases, anaphylaxis may continue or recur within 6 to 24 hours after being stung, and continued intensive treatment may be needed.²

If you had a previous systemic allergic reaction to a sting, you are at great risk of having a similar reaction if stung again.

Every systemic reaction to an insect sting should be considered a medical emergency. If you have a systemic allergic reaction, you should be observed in a clinic or emergency room afterwards to make sure you do not develop severe symptoms. If you have symptoms of a severe allergic reaction, seek immediate medical care by calling 911 or other emergency services.

You may also have another reaction to an insect sting that is not an allergic reaction (such as a toxic reaction or serum sickness).

Your health professional will diagnose an allergic reaction to insect stings by performing a physical examination and taking your medical history.

Your health professional may refer you to a specialist, such as an allergist (immunologist), who will perform allergy tests, such as skin tests or blood tests, to identify your allergies.

It is possible that you will not show any sensitivity to allergens in allergy tests even after you have had an allergic reaction to an insect sting.³ Your doctor may recommend that you repeat these tests in 3 months.

Key treatment points

• For normal reactions to insect stings, medical treatment is usually not needed. An ice pack or cold compress may reduce swelling and pain, along with taking a nonprescription pain reliever, such as acetaminophen.
• If you develop a large local reaction that spreads around the sting or affects an entire limb, taking an antihistamine can reduce your overall symptoms.
• Systemic allergic reactions involve your whole body and are considered a medical emergency. If you have had a severe systemic reaction to an insect sting in the past, carry an allergy kit with you so that, when stung, you can immediately treat yourself with the antihistamine tablet and epinephrine injection from the kit. Always seek emergency care after an epinephrine injection—your symptoms could reappear or become worse for several hours after the first epinephrine injection.
• If your systemic reaction gets worse, you may develop anaphylaxis, which is a life-threatening response to the insect venom. Emergency medical attention is needed; call 911 or seek immediate treatment in a hospital emergency room. Medications will be given to reduce swelling, open your airway to help you breathe, and stabilize your blood pressure.

Allergies to insect stings are treated by avoiding the insects that cause the allergy, treating mild cases with medications such as antihistamines, and understanding how and when to use an allergy kit for serious reactions.

Special care must be taken with children who have insect sting allergies. A child with a severe allergy may have life-threatening anaphylactic reactions to even tiny amounts of venom from the insect. Your child should always wear a medical alert bracelet and carry an allergy kit. Children at risk for severe allergic reactions should keep allergy kits at school or day care as well as at home. Make sure that all caregivers—such as school administrators, teachers, friends, and coaches—know about the insect sting allergy, where the allergy kit is kept, and how and when to give the epinephrine injection. Also, make sure they have a plan to transport your child to the hospital. Older, mature children should be taught to give self-injections.

Immediate treatment for an allergic reaction to an insect sting depends on the type and severity of your symptoms.

Normal reaction to insect stings

For the normal reaction that most people have to a sting, medical treatment is usually not needed. An ice pack or a cold compress and nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin or ibuprofen may relieve some of the swelling and pain, nonprescription pain relievers such as acetaminophen (for example, Tylenol) may reduce pain, and oral antihistamines such as diphenhydramine (for example, Benadryl) can reduce itching.

Large localized allergic reaction

Treatment for large local allergic reactions usually consists of:

• Cold compresses or ice packs, to reduce swelling and local pain.
• Elevating the limb (if this is where the sting occurred), to reduce swelling.
• Nonsteroidal anti-inflammatory drugs (NSAIDs), to reduce swelling and pain.
• Nonprescription pain relievers such as acetaminophen, to reduce pain.
• Antihistamines, which can reduce overall symptoms.
• Anesthetic creams or ointments, which may reduce pain and itching.
• Corticosteroids (such as prednisone), which can reduce swelling and pain; however, the use of corticosteroids to treat local allergic reactions is controversial.

Systemic allergic reactions

Systemic (whole-body) allergic reactions to a sting are considered a medical emergency. Immediate treatment is needed and may include:

• An injection of epinephrine.
• An antihistamine, which may be given along with the injection of epinephrine.
• Oral or intravenous (IV) corticosteroids.

How do I give myself an epinephrine injection?

How do I give my child an epinephrine injection?

Treatment for anaphylaxis—the most severe systemic allergic reaction, which can be life-threatening—is designed to keep your airway open and relieve other breathing or heart problems that can occur, especially if there are signs of shock. In addition to epinephrine and an antihistamine, treatment for anaphylaxis may include:

• Bronchodilators, to reduce breathing difficulties.
• Corticosteroids (such as prednisone), to help decrease inflammation.
• Intravenous (IV) fluids, to stabilize blood pressure.

If anaphylaxis is prolonged, medications to stabilize blood pressure and other measures to help with breathing—such as oxygen, intubation, and possibly a ventilator—may be needed.

If you had anaphylaxis, you will normally need to remain in the hospital for 8 to 12 hours before being released. Symptoms of anaphylaxis can recur after several hours, so you may need additional medication or treatment.

Long-term treatment

If testing and examinations confirm you are allergic to insect stings, long-term treatment usually includes:

• Avoiding or preventing stinging insects. You can reduce your chances of being stung by avoiding areas where insects nest; wearing shoes, long sleeves, and long pants when outdoors; and not wearing perfume or scented lotions.
• Carrying an allergy kit. The kit contains emergency medication, including antihistamine tablets and an epinephrine injection that you can immediately self-administer if you are stung. Talk with your doctor about how to store your kit and when and how to give yourself the injection.
• Wearing a medical alert bracelet or medallion. You can purchase a medical alert bracelet or other jewelry that lists your insect sting allergies through most pharmacies or on the Internet. Medical alert jewelry quickly alerts emergency response workers to your allergy, which helps them provide immediate and appropriate treatment.

How do I give myself an epinephrine injection?

How do I give my child an epinephrine injection?

If you have a history of systemic allergic reactions, you may consider treatment with a series of shots (immunotherapy) to reduce your sensitivity to the stinging insect's venom and lower your risk of a severe reaction. Immunotherapy is usually not needed for adults or children who have only a large local reaction to a sting. But anyone who experiences increasingly severe large local reactions with each new sting may want to consider immunotherapy. Talk with your doctor or allergy specialist to see whether immunotherapy is appropriate for you.

Should I have allergy shots (immunotherapy) for allergies to insect stings?

Knowing which insect venom triggers your allergies and avoiding those insects is the best way to avoid allergic reactions to the stings. Unfortunately, it can be difficult to avoid insects, especially if you spend time outdoors.

Home treatment for allergic reactions to insect stings usually includes:

• Avoiding or preventing exposure to stinging insects, such as not using scented lotions or perfume, not wearing brightly colored clothing, and not going barefoot when you are outdoors.
• Learning what types of stinging insects you are allergic to, including how to identify them and where they live, so you can better avoid them.
• Carrying an allergy kit containing emergency medications you can use if stung. Make sure you keep the supplies fresh and know how and when to properly use them. You need to have an allergy kit with you at all times. Check your kit regularly and replace medications that have passed the expiration dates. Allergy kits with doses appropriate for children are available. Children at risk of severe allergic reactions should keep kits at school or day care as well as at home.
• Wearing a medical alert bracelet or medallion that lists your insect sting allergies, to alert emergency response workers if you have a severe allergic reaction. Medical alert jewelry can be ordered through most pharmacies or on the Internet.

Educate yourself and others

• If you or your child is allergic to insect stings, know what those particular insects look like and where they live.
• Make sure that all caregivers—such as school administrators, teachers, friends, and coaches—and coworkers know about the insect sting allergy, know what the symptoms look like during an allergic reaction, know where the allergy kit is kept and how to give the epinephrine injection, and have a plan to transport you or your child to the hospital.
• Teach older, mature children how to give self-injections.

What to do if you are stung

• Move away from the stinging insect and leave the area immediately—there may be a nest nearby.
• Remain as calm and quiet as possible. Movement will increase the spread of venom in the bloodstream.
• Remove the stinger from your skin immediately (see how to remove a stinger). It may be best to scrape or flick the stinger off your skin—squeezing or gripping the stinger to pull it out may inject more venom into your wound.
• Lower your arm or leg (if you have been stung in a limb) to slow the spread of venom. If the limb later becomes swollen, you can try elevating the affected leg or arm.

For normal, local sting reactions and large local allergic reactions, try:

• Using a cold compress or ice pack to reduce swelling. Elevating the affected part of the body may also help reduce swelling.
• Taking a nonprescription pain reliever (analgesic) for pain, such as aspirin, acetaminophen (for example, Tylenol), or isometheptene mucate (Midrin). Do not give aspirin to anyone younger than age 20, unless it is prescribed by a doctor, because of the risk of Reye's syndrome.
• Taking an antihistamine to help reduce your symptoms. Read and follow any warnings on the label.

Emergency care for a severe allergic reaction

Any systemic reaction (anaphylaxis) to an insect sting should be considered a medical emergency. If you have symptoms of a severe allergic reaction—such as difficulty breathing, dizziness, swelling of your tongue or throat, or abdominal cramps—call 911 or other emergency services immediately.

If your doctor has prescribed an allergy kit, use the kit if:

• You have been taught how and when to use it.
• Your symptoms are severe.
• You have a kit immediately available.
• You have had a severe reaction in the past from a sting from the same type of insect, and similar symptoms are developing.

Antihistamines can help reduce your symptoms. But antihistamines may not be strong enough for severe reactions. Even though it can be scary to give yourself an epinephrine shot, it may be the only way to stop a severe reaction.

Organizations

• Allergic Reaction
• Insect Bites and Stings and Spider Bites
• Rash, Age 11 and Younger
• Rash, Age 12 and Older
• Shock

Citations

1. American Academy of Allergy, Asthma, and Immunology (2000). Allergy Report. Milwaukee: American Academy of Allergy, Asthma and Immunology. Also available online: http://www.theallergyreport.org/reportindex.html.

2. Golden DB (2003). Stinging insect allergy. In NF Adkinson Jr et al., eds., Middleton's Allergy Principles and Practice, 6th ed., vol. 2, pp. 1475–1486. Philadelphia: Mosby.

3. Golden DBK, et al. (2001). Insect sting allergy with negative venom skin test responses. Journal of Allergy and Clinical Immunology, 107(5): 897–901.

Other Works Consulted

• Ross RN, et al. (2000). Effectiveness of specific immunotherapy in the treatment of hymenoptera venom hypersensitivity: A meta-analysis. Clinical Therapeutics, 22(3): 351–358.

Author:	Colleen Cronin	Last Updated February 1, 2006
Medical Review:	Kathleen Romito, MD - Family Medicine Harold S. Nelson, MD - Allergy and Immunology
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