Types of Allergies

Insect Venom

Stings from five insects - honeybees, hornets, wasps, yellow jackets and fire ants - are known to cause allergic reactions to the venom injected into the skin. While most people are not allergic to insect venom, the pain from a sting may cause them to mistake a normal reaction for an allergic one. Knowing the difference between a normal reaction and an allergic reaction might save you a trip to the doctor’s office.

Overview

Insect stings typically result in pain, swelling and redness confined to the sting site. More severe reactions include symptoms appearing over a wider area (for example, swelling of your whole arm if you were stung on your wrist) or affecting other parts of the body from where the sting occurred.

Allergic reactions to stings can occur even after many normal reactions to stings and at any age. It has been estimated that potentially life-threatening allergic reactions to insect venom occur in 0.4 percent to 0.8 percent of children and 3 percent of adults. Insect sting reactions account for at least 40 deaths each year in the United States.

The majority of insect stings in the United States come from wasps, yellow jackets, hornets and bees. The red or black imported fire ant now infests more than 260 million acres in the southern United States, where it has become a significant health hazard and may be the number one agent of insect stings. While there are native fire ant species, the species that causes the most problems for us were accidentally imported to the United Stated from South America.

Insect Sting Allergy Symptoms

  • Pain
  • Redness
  • Swelling (in area of sting and sometimes beyond)
  • Flushing
  • Hives
  • Itching
  • Anaphylaxis (less common), a potentially life-threatening reaction that impairs breathing and can cause the body to go into shock

For more information on insect sting allergy symptoms click here.

Insect Sting Allergy Management and Treatment

  • Avoid insects.
  • Immediately inject epinephrine (adrenaline) if symptoms of anaphylaxis develop.
  • Consider allergy shots (immunotherapy).

For more information on insect sting allergy management and treatment click here.

Symptoms

The stings of five insects - honeybees, hornets, wasps, yellow jackets and fire ants - are known to cause allergic reactions. The severity of an insect sting reaction varies from person to person and from one sting to the next. You may not experience an allergic reaction until you have been stung several times.

There are three types of reactions that can occur:

A normal local reaction will result in pain, swelling and redness confined to the sting site.

A large local reaction will result in swelling well beyond the sting site. For example, a sting on the forearm could cause the whole arm to swell - a condition that usually peaks two to three days after the sting and can last a week or more.

A systemic allergic reaction is the most serious and requires medical attention. Symptoms of a systemic allergic reaction can range from mild to severe. They may include the following (either alone or in combination):

  • Hives
  • Itchiness
  • Flushing
  • Swelling in areas away from the sting
  • Dizziness or a sharp drop in blood pressure
  • A hoarse voice, swelling of the tongue or difficulty swallowing
  • Hives, itching and swelling in areas other than the sting site
  • Abdominal cramping, vomiting, intense nausea or diarrhea
  • Unconsciousness or cardiac arrest

Anaphylaxis - a severe life-threatening allergic reaction that impairs breathing, causes a sudden drop in blood pressure and can send the body into shock - can occur within minutes of a sting. A dose of epinephrine (adrenaline), typically administered in an auto-injector, and immediate medical attention are required.

People who have already experienced a systemic allergic reaction to an insect sting are at risk of a similar or worse reaction if they are stung again. Those who have had a possible systemic allergic reaction to an insect sting should carry two epinephrine auto-injectors and see aboard-certified allergist.

Diagnosing Insect Sting Allergy

If you are concerned that you may have an allergy to insect venom, see an allergist.

Your allergist should take a detailed medical history, including questions about previous stings (how many there have been and where you were stung), your reaction to those stings (what you experienced, how long the reaction lasted and what you did to get relief) and any additional symptoms.

Your allergist may diagnose an allergy to insect venom through a skin-prick test, a blood test or an intradermal skin test.

In the skin-prick test, a small amount of a liquid containing insect venom is placed on the back or forearm, which is then pricked with a small, sterile probe to allow the liquid to seep into the skin. If a raised, reddish spot forms within 15 to 20 minutes, that can indicate an allergy. In the blood test, a blood sample is sent to a laboratory to test for the presence of immunoglobulin E (IgE) antibodies to insect venom.

If the results are inconclusive (for example, if your skin-prick or blood test is negative, but your medical history indicates that you have had an allergic reaction), your allergist will likely recommend an intradermal skin test, in which a small amount of venom extract is injected just under the skin. The site is examined after about 15 minutes for signs of an allergic reaction. This test is considered more accurate than the skin-prick or blood tests in determining the presence of IgE antibodies.

The strength of a reaction to a skin or blood test does not indicate how severe your allergic reaction will be the next time you are stung.

Management and Treatment

Bees, wasps, hornets and yellow jackets are found throughout the United States and are most active during late summer and early fall. The red or black fire ant, found mainly in the southern United States, is a serious health hazard year-round. Avoidance of insect stings is the first line of defense. Here are some proven strategies:

  • Don’t walk barefoot in the grass, where stinging insects forage.
  • Don’t drink from open soft drink cans; stinging insects are attracted to them and may crawl inside.
  • Keep food covered when eating outdoors.
  • Don’t use sweet-smelling perfume, hairspray or deodorant.
  • Avoid wearing brightly colored clothing with flowery patterns.
  • Wear long pants, long-sleeved shirts, socks, shoes and work gloves when working outdoors.
  • Be cautious near bushes, eaves and attics, and avoid garbage containers and picnic areas.
  • Have a professional exterminator remove known nests and inspect for other potential nesting areas.

For emergency treatment, an allergist can prescribe and give instructions on how to use an epinephrine auto-injector. A person who has had a systemic allergic reaction to an insect sting has an increased risk of having a similar or worse reaction if stung again and should always have two epinephrine auto-injectors close at hand. The risk of an allergic reaction can persist for a long time, even when the systemic allergic reaction was many years earlier.

Epinephrine is the only approved treatment for anaphylaxis. A delay in using epinephrine has been shown to increase the risk of death. For long-term protection, an allergist can treat the allergic person with allergy shots (immunotherapy), which build tolerance over time through gradually increasing doses of purified insect venom. Venom immunotherapy significantly reduces the risk of a systemic reaction to future stings. The length of venom immunotherapy is usually three to five years, but it can be continued indefinitely depending on the severity of past reactions and the risk to the patient of future stings.

Fire ant sting allergy treatment

Fire ant sting allergy is treated in a two-step approach:

  • The first step is the emergency treatment of the symptoms of a serious reaction when they occur;
  • The second step is preventive treatment of the underlying allergy with whole body extract immunotherapy.

Life-threatening allergic reactions can progress very rapidly and require immediate medical attention. Emergency treatment usually includes administration of certain drugs, such as epinephrine, antihistamines, and in some cases, corticosteroids, intravenous fluids, oxygen and other treatments. Once stabilized, these patients sometimes require close observation in the hospital overnight.

Injectable epinephrine is often prescribed as emergency rescue medication for treating an allergic reaction. People who have had previous allergic reactions and rely on epinephrine must remember to carry it with them at all times. Also, because one dose may not be enough to reverse the reaction, immediate medical attention following a fire ant sting is recommended.

What is a normal reaction to a fire ant sting, and how is it treated?

The severity of a fire ant sting reaction varies from person to person. One of the main differences between fire ants and other insects is that a usual sting event consists of multiple fire ants stinging. This is because when a fire ant mound is disturbed hundreds to thousands of fire ants respond. In addition, each ant can sting repeatedly. Each ant will bite and hold on with its mandibles (jaw) and sting several times. If not removed, this results in a little semi-circular pattern of stings. Since fire ants hold on with their mandibles, they often have to be pulled off individually and are not easily brushed off when they are stinging.

Almost all people stung by fire ants develop an itchy, localized hive or lump at the sting site, which usually subsides within 30 to 60 minutes. This is followed by a small blister within four hours. This usually appears to become filled with pus-like material by eight to 24 hours. However, what is seen is really dead tissue, and the blister has little chance of being infected unless it is opened. When healed, these lesions may leave scars.

Fire ant sting treatment is aimed at preventing secondary bacterial infection, which may occur if the pustule is scratched or broken. Clean the blisters with soap and water to prevent secondary infection. Do not break the blister. If a blister is accidently opened, careful attention to keeping the area clean with soap and water should still prevent infection. Topical corticosteroid ointments and oral antihistamines may relieve the itching associated with these reactions.

What is whole body extract immunotherapy?

The long-term treatment of fire ant sting allergy is called whole body extract immunotherapy, that contains the entire body of the ant, not just the venom, as is the case with other stinging insects. It is a highly effective program administered by an allergist-immunologist, which can prevent future allergic reactions to fire ant stings. At this time, we are not able to milk venom from fire ants.

Whole body extract immunotherapy involves administering gradually increasing doses of extract to decrease a patient’s sensitivity to the fire ant sting. This can reduce the risk of a future allergic reaction to that of the general population. In a matter of weeks to months, people who previously lived under the constant threat of severe reactions to fire ant stings can return to leading normal lives.

If you think you might be allergic to fire ant stings, see an allergist. Based on your past history and certain tests, the allergist will determine if you are a candidate for skin testing and immunotherapy.

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