Insect Sting Allergy

• Several insects belonging to the class Hymenoptera are capable of injecting venom into humans and animals. These insects include honeybees, bumble bees, hornets, wasps, yellow jackets, and fire ants.
• All of these insects are currently found in the United States as well as in most other land areas of the globe. Their venom, which they use to kill or paralyze other insects, is composed of proteins and other substances. It is proteins in the venom that cause allergic reactions in people.
• Not everyone is allergic to stinging insect venom. In people who are not allergic, the venom causes only redness, itching, and mild pain and swelling at the site of the bite. Cleaning the area and applying ice are enough to relieve the symptoms.
• Even people who are allergic to the venom usually have only mild symptoms, although the swelling may extend beyond the area right around the sting. People with allergies may have a more serious reaction, called an anaphylactic reaction.

An allergic reaction occurs when the immune system of the body overreacts to an "invader" such as insect venom (the allergen). This overreaction is sometimes referred to as a hypersensitivity reaction.

The white blood cells produce an antibody to the protein in the venom.

• The allergic reaction occurs when the antibody, known as immunoglobulin E, or IgE, comes in contact with the protein, either at the first sting or later.
• IgE promotes release from certain cells of chemicals and hormones called "mediators." Histamine is an example of a mediator.
• It is the effects of these mediators on organs and other cells that cause the symptoms of the allergic reaction.

Ants, bees, and wasps have a stinger or venom sac and gland on their tail that they use to inject venom.

• Several stings may occur, particularly if you accidentally disturb a hive or nest.
• This is particularly true with fire ants and so-called Africanized bees.
• Africanized bees are the result of breeding of domesticated and wild honeybees in Africa that resulted in a very aggressive honeybee. The venom of these bees is no more potent than that of normal honeybees, but their aggressive nature increases the likelihood that they will swarm and sting you many times, sometimes hundreds of times.
• Such a large number of stings may result in serious reactions or death, even if you are not allergic to bee venom.
• If you are allergic to the venom, then you may have an allergic reaction from even a single sting. This is called an anaphylactic reaction. It can be dangerous, even life threatening.

An anaphylactic reaction does not usually occur on the first sting.

• The immune system makes the antibody at the first sting and stores it on special cells until the next sting. This is called "sensitization."
• At the first sting, therefore, the body does not have antibodies specific to the venom.
• Only on a second or later sting can the body mount a major defense against the venom.
• This is when a life-threatening anaphylactic reaction may occur.
• Anaphylactic reactions are rare, and do not happen to every person who is stung by an insect.
• When an anaphylactic reaction seems to occur on the very first sting, probably the person was stung before without realizing it.

Insect venom is used to treat certain medical conditions.

• In Chinese herbal medicine, the venoms of various insects in this class are used either as direct stings (as a treatment for arthritis and other chronic diseases) or are applied to the skin or the eyes.
• Such apiotherapy (the medicinal use of honeybee products) may result in an anaphylactic reaction in people who are allergic.
• Allergy shots given by an allergy specialist also contain venom but are specifically designed to be given to allergic people to reduce their sensitivity to the allergen.

Most insect stings cause some pain and swelling in the area of the sting, called a local reaction.

• People who are allergic to bee stings or who have been stung many times may react more dramatically.
• A severe local reaction may lead to pain and swelling that increase over the next few hours and becoming very uncomfortable. This does not constitute an anaphylactic reaction. The reaction must involve at least two of your body's organ systems (such as lungs and heart) to qualify as an anaphylactic reaction.
• Although most local reactions are not serious, if they are near the face or neck, swelling can quickly block the airway and cause serious problems.

Fire ant stings

• Fire ant stings cause a reaction in almost everyone.
• Itchy hives usually form at the site immediately and recede within an hour.
• A small blister forms at each site within 4 hours.
• Within 8-24 hours, a small sore with pus forms at each sting site. The area around the sores may feel burning and itchy. The pus does not mean the sore is infected.
• The sores rupture within 72 hours. The itching, pain, and redness may last for several days but should improve gradually.
• Worsening redness, pain, swelling, and warmth may signal an infection at the site. If this occurs, see your health care provider right away.

Symptoms over the entire body are always a concern because they may signal an anaphylactic reaction. If these reactions progress, they may lead to death, sometimes within a matter of minutes. These reactions may include the following:

• Hives (swollen bumps on the skin)
• Significant swelling over major body parts: face, head, neck, arms/hands, legs/feet
• Difficulty breathing, wheezing, or the feeling that the throat is closing
• Dizziness or fainting
• Chest pain or racing heartbeat
• Nausea, vomiting, or diarrhea

The dizziness and fainting are due to a dangerously low blood pressure. This condition is known as "shock," and anaphylaxis is often called anaphylactic shock.

Mild localized itching, swelling, or discomfort requires a call your health care provider for advice.

Worsening of local symptoms over a few days may be evidence of infection at the sting site. Pain, increased swelling and redness, and warmth suggest an infection. Call your health care provider for an appointment the same day.

If you had a reaction in the past, even if you used an epinephrine injection kit for this sting, go immediately to your medical office or hospital emergency department, whichever is closer. Even if you have treated yourself, you still need to be evaluated to make sure that your symptoms are resolving and are not recurring.

Hives or rash or swelling all over your body, difficulty breathing or swallowing, or dizziness or fainting suggest an anaphylactic reaction and require immediate medical attention.

• If you have these severe symptoms or symptoms over your entire body, you should go to a hospital emergency department.
• Do not drive yourself to the hospital.
• If no one is available to drive you right away, call 911 for emergency medical transport. If you are able, tell the dispatcher that you are having a reaction to a sting.
• While waiting for the ambulance, take self-treatment measures.

One or more prior severe reactions to an insect sting place you at an increased risk of severe reactions with each sting.

• It is important to let the health care provider know that you have been stung and whether you have had reactions in the past.
• Be prepared to tell the health care provider all of the medications you have taken for the sting, both prescription and over-the-counter. Don't forget any herbal preparations or other treatments you may have taken.
• Physical examination is the most important part of the evaluation of insect stings.
• Your blood pressure and pulse will be checked to make sure you are not in shock.
• Examination should also include the skin for swelling and hives, the lungs for wheezing, and the upper airway for possible swelling or obstruction.

An ECG or chest X-ray may be helpful but is not needed in every case. Laboratory tests are usually not helpful.

For most insect stings, home care is all that is necessary.

• If insects are on or around you, remain calm.
  • Gently brush any insects from your skin.
  • Quietly leave the area as quickly as you can.
• If the stinger is still lodged in the skin, as it usually is after honeybee stings, it should be removed promptly.
  • You can do this by scraping the site with a credit card or similar device, perpendicular to the skin. A fingernail can be used.
  • Pinching the stinger to pull it out is not advised, because this may inject more venom.
• Control local swelling
  • Elevate the part of the body where the sting is located.
  • Apply ice to the area of the sting.
  • If the sting is on the hands or feet where rings or other tight-fitting jewelry is worn, these should be removed immediately before swelling develops, to avoid any compression of the blood supply to these areas.
• Control pain: Ibuprofen (Advil) or acetaminophen (Tylenol) is usually sufficient to relieve pain.
• Treat the itch
  • Take an antihistamine pill, such as diphenhydramine (Benadryl). This helps counteract one of the mediators of the reaction and will help control itching. Diphenhydramine is available without a prescription. Caution - this medication makes most people too drowsy to drive or operate machinery safely. It can be taken every 6 hours for the first few days, until the swelling begins to improve.
  • Hydrocortisone cream, available over-the-counter, can be applied to the site of the insect sting to relieve itching.
  • A paste of baking soda or salt and water, rubbed on the skin, may provide relief.
  • An over-the-counter lotion such as Calamine can help.
  • If a blister develops at the site, keep the area clean but do not break the blister.

Do not be alarmed if the reaction takes 2-5 days to heal. Continue treatment until all symptoms are gone.

For more severe reactions, self-treatment is not recommended. Call your health care provider or 911, depending on the severity of your symptoms. Do not attempt to drive yourself. If no one is available to drive you right away, call for an ambulance. If you have symptoms of anaphylaxis, here's what you can do while waiting for the ambulance:

• Try to stay calm.
• Remove yourself from the area where the insects are.
• Take an antihistamine (1-2 tablets or capsules of diphenhydramine [Benadryl]) if you can swallow without difficulty.
• If you are wheezing or having difficulty breathing, use an inhaled bronchodilator such as albuterol (Proventil) or epinephrine (Primatene Mist) if one is available. These inhaled medications dilate the airway.
• If you are feeling light-headed or faint, lie down and raise your legs higher than your head to help blood flow to your brain.
• If you have been given an epinephrine kit, inject yourself as you have been instructed. The kit provides a premeasured dose of epinephrine, a prescription drug that rapidly reverses the most serious symptoms (see Follow-up).
• Bystanders should administer CPR to a person who becomes unconscious and stops breathing or does not have a pulse.
• If at all possible, you or your companion should be prepared to tell medical personnel which medications you have taken today, which you usually take, and any known allergies.

The top priority for the medical team is ensuring that your breathing and blood pressure are protected.

• If you are having difficulty breathing, you may be given oxygen via a tube in your nose or by face mask.
• In cases of severe respiratory distress, you may be put on a mechanical ventilator. This is temporary until the effects of the reaction abate.
• If your blood pressure is too low, an IV line will be placed.
• You may be given saline solution through the IV to boost your blood pressure.
• You may be given medication if needed to ease your breathing and/or increase your blood pressure.

• Epinephrine is the most important treatment and may be lifesaving. Epinephrine is usually given as an injection.
• H1 type antihistamine such as diphenhydramine (Benadryl) usually is given by mouth or injection to decrease the histamine reaction. This relieves the itching.
• H2 type antihistamine (H2-blocker), such as ranitidine, famotidine, or cimetidine, may be given to augment the effect of diphenhydramine.
• Corticosteroids, such as prednisone or methylprednisolone (Solu-Medrol), are often given to decrease swelling and suppress the immune response.
  • If you are given antihistamines and steroids, you may be advised to continue to take them by mouth for several days after you leave the hospital.

For more information on allergy medications, see Allergy and Hay Fever Medications.

Allergy shots (immunotherapy) may be effective in people with severe reactions to certain insect stings.

• Allergy shots are given in a series over several months to build up to a maintenance dose that is continued monthly for 3 to 5 years.
• Each shot contains a little bit more of the insect venom antigen.
• Ideally, the person becomes desensitized to the antigen over time.
• Shots are effective at reducing the severity of the reaction in most people.
• These shots are available for bee and fire ant venoms.

Make sure that all of your health care providers are aware of the type of reaction you have had.

If you have had a severe or all-over reaction, you should be given a prescription for an epinephrine injection kit (EpiPen, Auvi-Q) when you leave the hospital.

• This is a premeasured dose of epinephrine in an easy-to-use syringe.
• You would inject yourself in the thigh muscle with the epinephrine at the first sign of a reaction.
• Someone at your medical office can show you how to use the kit. Clear instructions are also provided at the web site of the Food Allergy & Anaphylaxis Network.
• It is recommended that you keep 2 or more of these kits at different locations and that you keep one with you at all times in case of a sting.

If you have a severe or all-over reaction to an insect sting, you should see an allergy specialist (allergist). Desensitization therapy is available for some types of venom allergies.

Take precautions to avoid insect stings in the future.

• Avoid nests or hives of stinging insects.
• Do not wear bright clothing or perfumes that might attract bees and wasps.
• Remain calm and quiet around flying insects. Move slowly.
• Take special care when around food or drinks outdoors, as at cookouts or picnics. Stinging insects are attracted to foods, especially sweet foods such as soft drinks.

Evaluation by an allergist for desensitization injections has been shown to be of benefit.

Obtain one or more epinephrine injection kits if this has been prescribed for you.

• Keep the kit(s) in convenient locations and have one near you at all times.
• Read the instructions right away and review them often.
• It is important that you be able to get to the kit and use it quickly in case of a reaction.
• Make sure your family members and closest friends know how to use the kit as well.
• Any time this device is used, you must go immediately afterward to your health care provider or to a hospital emergency department.

Prompt treatment usually avoids any short-term complications, but any delay in the treatment of a severe allergic reaction can result in rapid deterioration and death.

The long-term outlook is usually good as well. Local infection at the sting site can occur but is rare.

Arthritis, kidney failure, or nervous system disorders are late complications of a sting (weeks or possibly months later).

• This is extremely rare.
• If you have joint pain or swelling, urinary problems, or unexplained numbness, tingling or burning sensation, or pain in the weeks after an insect sting, you should see your health care provider.

If you develop anaphylactic shock following an insect sting, you are at an increased risk of developing anaphylaxis in the future if you are stung again.