An allergic reaction to an insect sting occurs when the immune system overreacts to the insect's venom. The leukocytes (white blood cells) of an allergic individual produce an antibody called immunoglobulin E (IgE), which attaches to the protein in the venom. This triggers the release of histamine and other chemicals that cause allergic symptoms, which often include redness, swelling and itching at the site of the sting.
About 15% of adults in the United States exhibit mild, localized allergic reactions to insect stings. For a small number of people who are severely allergic to insect venom, insect stings can be life threatening. More than 500,000 people enter hospital emergency rooms every year as a result of insect stings. A severe allergic reaction known as anaphylaxis occurs in 0.5-5% of the U.S. population as a result of insect stings. Insect sting anaphylaxis causes at least 40 deaths in the United States each year.
The honeybee, yellowjacket, paper wasp, white-faced hornet (bald-faced hornet) and fire ant are among the most common insects that trigger insect sting allergies. Since the stinger is a modified egg-laying apparatus, only females can sting.
TYPES OF STINGING INSECTS
Honeybee: Honeybees are a subset of bees, which fall into the Order Hymenoptera and Suborder Apocrita. Out of the 20,000 known species of bees, four are considered honeybees -
Apis florea, Apis dorsata, Apis cerana and Apis mellifera. The honeybee is covered with short, dense hair, usually golden-brown and black, and it has a striped abdomen. They are typically found near flowers and flowering trees. Honeybees are much less aggressive than wasps and hornets.
Yellowjacket: Yellowjackets are black-and-yellow wasps of the genus Vespula or Dolichovespula. They can be identified by their distinctive combination of black-and-yellow color, small size (slightly larger than a bee) and entirely black antennae. They are attracted to human food, including fruit, sugar and meat. Yellowjackets are the most prevalent in the south.
Paper wasp: Paper wasps belong to the family Vespidae. They are dusty yellow to dark brown or black in color, and they have little to no hair. They make small umbrella-shaped combs, which hang horizontally in protected spaces like eaves, soil cavities or attics.
White-faced hornet (bald-faced hornet): The white-faced hornet is not a true hornet. It is more closely related to another type of wasp called the yellowjacket than it is to hornets like the European hornet. It belongs to the Vespidae family. These aggressive insects build large paper nests that hang upside down from tree branches.
Fire ant: Fire ants nest in the soil, usually near moist areas such as riverbanks, pond edges and watered lawns. A single nest is usually less than a square yard, and it may have several small openings on the surface. Fire ants have a coppery-brown head and body, with a darker abdomen. The ants can be distinguished by their aggressive behavior, especially near the nest. Fire ants feed mostly on young plants, seeds and sometimes crickets. Fire ants are the most prevalent in the south.
Symptoms vary from person to person and from insect to insect. Redness, swelling and itching at the site of the sting are the most common symptoms. Some individuals experience a large amount of swelling near the site of the sting.
Fire ants cause an allergic reaction in almost everyone. Itchy sores usually form immediately at the site of the sting and slowly clear up after an hour. After about four hours, a small blister forms at each sting site. Between eight and 24 hours later, a small, pus-filled sore forms. The area around the sore may burn and itch. The sore will rupture within 72 hours. The itching, pain and redness may last several days, but should gradually improve. If redness, pain or swelling becomes worse, it may be a sign of infection and a healthcare provider should be consulted.
The allergic reactions of adults and children should be evaluated differently. For instance, research shows that children who experience skin reactions like hives or swelling to an insect bite are not at high-risk for life-threatening reactions. However, adults who experience more than a local reaction should be evaluated for insect allergy and consider immunotherapy if they are allergic.
For a small number of people who are severely allergic to insect venom, insect stings can cause a life-threatening reaction known as anaphylaxis. Anaphylaxis is a systemic reaction, which means that many parts of the body are affected.
The time lapse between the insect sting and anaphylactic symptoms varies among individuals. Symptoms can appear immediately or can be delayed from 30 minutes to one hour after exposure. Symptoms may also disappear and then recur hours later. Once symptoms arise, they progress quickly.
Symptoms of anaphylaxis can vary from mild to severe and are potentially deadly. The most dangerous symptoms are low blood pressure, breathing difficulties, shock and loss of consciousness, all of which can be fatal.
Symptoms of anaphylaxis may include itching and hives over large areas of the body, swelling in the throat or tongue, difficulty breathing, dizziness, diarrhea, stomach cramps, chest pain or tightness, cardiac arrest, faint pulse, flushing, angioedema (swelling beneath the skin), trouble swallowing, respiratory arrest, rash, itchy mouth/throat, anxiety, hay fever-like symptoms, red/itchy/watery eyes, headache, nausea or diarrhea. Histamine can induce vasodilatation of arterioles and constriction of bronchioles in the lungs, also known as bronchospasm. In severe cases, a rapid drop in blood pressure may cause shock and loss of consciousness.
Anaphylaxis is a medical emergency and treatment must be administered as soon as possible. Epinephrine is a medication used to treat severe allergic reactions that can result in anaphylaxis. Administering the epinephrine as soon as possible improves the chances of survival and a quick recovery. Epinephrine opens the airways and raises the blood pressure by constricting blood vessels. Patients may also be admitted to the hospital to have their blood pressure monitored and to possibly receive breathing support.
Other emergency interventions may also include endotracheal intubation (placing a tube through the nose or mouth into the airway) or emergency surgery to place a tube directly into the trachea (tracheostomy or cricothyrotomy).
Hypotension (low blood pressure) is usually treated with intravenous fluids and sometimes with vasoconstrictive medications also referred to as "pressors."
Bronchodilator drugs like Albuterol© are used to treat bronchospasm.
After epinephrine and/or other lifesaving measures are taken, antihistamines (like diphenhydramine) and corticosteroids (like prednisone) may be given to further reduce symptoms.
Individuals with a history of anaphylaxis should carry an autoinjectable epinephrine device (known as an EpiPen©) with them at all times.
A toxic reaction can cause symptoms similar to those of an allergic reaction, including nausea, fever, swelling at the sting site, fainting, seizures, shock and even death. A toxic reaction occurs when the insect venom acts like a poison in the body. This reaction may happen after only one sting, but it usually takes many stings from insects that are not normally considered poisonous.
Symptoms vary depending on the type of insect, the toxicity of the venom and the amount of venom injected. Symptoms may include diarrhea, fever, weakness, lightheadedness, rapid swelling at the site of the sting, muscle spasm, headache, drowsiness, fainting, seizures, nausea and vomiting. In most cases, symptoms resolve within 48 hours. Toxic reactions are rarely serious, but they occasionally sensitize children, making them prone to future allergic reactions.
A life-threatening toxic reaction can occur after more than 50 stings in children and after 100-500 in adults. Individuals should seek medical help immediately if symptoms are severe. In severe cases, patients may be treated with epinephrine.
It is possible to have both a toxic reaction and an allergic reaction at the same time.
Serum sickness is a rare reaction to a foreign substance in the body that can cause symptoms hours or days after the sting. Patients may experience fever, joint pain, hives and flu-like symptoms. Patients who experience symptoms of serum sickness should consult a qualified healthcare provider. Patients who have serum sickness usually recover completely within 7-28 days.
Antihistamines like diphenhydramine HCL (Benadryl©) may be used to relieve itching that is associated with serum sickness. Corticosteroids like prednisone (Deltasone©, Orasone© or Sterapred©) have been used to reduce inflammation associated with serum sickness. Treatment usually lasts about two weeks. Doses should gradually decrease as symptoms clear up. Symptoms may reappear in severe cases if steroids are stopped too quickly. NSAIDs like ibuprofen (Motrin© or Advil©) may be used to decrease inflammation and reduce fever.
Local allergic reaction: Elevate the affected extremity and apply ice or a cold compress to reduce swelling and pain. Gently clean blisters or sores with soap and water to prevent secondary infections. Do not break blisters. Topical steroid ointments or oral antihistamines like diphenhydramine HCL (Benadryl©) should relieve itching. Consult a healthcare provider if swelling worsens or if the sting site seems infected.
Honeybee sting: When honeybees sting, they leave their stingers behind. If the bee's stinger is left inside the skin, remove it within 30 seconds in order to avoid absorbing more venom. The stinger can easily be removed by scraping it with a fingernail or plucking out with tweezers. Avoid squeezing the sac because it will force more venom through the stinger and into the skin.
Hornets, wasps and yellow jackets: Hornets, wasps and yellow jackets do not leave their stingers inside the skin. Unlike honeybees, these insects do not die after they sting, and they are capable of stinging multiple times. Remain calm and brush these insects from the skin promptly with deliberate movements to prevent additional stings.
Fire ant sting: Carefully brush the fire ants off to prevent repeated stings, and leave the area. Fire ant stings usually cause blisters to form about 24 hours after the sting. Up to 50% of patients develop large local reactions at the site of fire ant stings. Swelling may last for several days and may be accompanied by itching, redness and pain. Clean the sting sites with soap and water and do not break the blisters. The sores will heal in seven to 10 days. Diabetics and individuals with circulatory disorders, including varicose veins and phlebitis, are at an increased risk for complications and should consult a healthcare provider after being stung.
Epinephrine: Epinephrine is a medication used to treat severe allergic reactions that result in anaphylaxis. Administering the epinephrine early in anaphylaxis improves the chances of survival and a quick recovery. Individuals with a history of anaphylaxis should carry an autoinjectable epinephrine (known as an EpiPen©) with them at all times. After administering an EpiPen©, patients should consult a healthcare provider.
H1 type antihistamine: H1 type antihistamine, like diphenhydramine (Benadryl©), is usually administered orally or injected into the bloodstream to decrease the histamine reaction and relieve the itching associated with insect stings.
H2 type antihistamine (H2-blocker): H2 type antihistamine (H2-blocker), like ranitidine, famotidine or cimetidine, may be administered to enhance the effect of diphenhydramine.
Corticosteroids: Corticosteroids, like prednisone or methylprednisolone (Solu-Medrol©), are often administered to help decrease swelling and suppress the immune response.
: Currently, there is insufficient evidence available on the safety and effectiveness of integrative therapies for the prevention or treatment of insect sting allergy. Insect stings can cause a life-threatening reaction known as anaphylaxis. The integrative therapies listed below should be used only under the supervision of a qualified healthcare provider, and should not be used in replacement of other proven therapies or preventive measures.
Unclear or conflicting scientific evidence
: Andiroba oils have been traditionally used to make insect repellant based soaps and candles.
Use cautiously in patients with known allergies or known sensitivities to andiroba, Carapa spp., or its constituents. Avoid in patients with known dermatologic sensitivities, as well as in newborns and infants.
: Early studies have assessed the efficacy of catnip oil or its constituents as an insect repellent against mosquitoes. These studies have yielded promising results, however, further research is needed to obtain additional data on the level of effectiveness of catnip oil for this application.
Avoid if allergic or hypersensitive to catnip, its constituents, or members of the Lamiaceae family. Use cautiously with psychiatric disorders or if taking medications that affect the central nervous system. Avoid if pregnant or breastfeeding.
: Limited available clinical study has examined the effectiveness of a topical combination product containing stinging nettle for insect bites. Results did not show a significant reduction in erythema or itching with the nettle-containing cream. Further well-designed clinical trials are required before a firm conclusion can be made.
Avoid if allergic or hypersensitive to nettle, the Urticaceae family, or any ingredient of nettle products. Use cautiously with diabetes, bleeding disorders, and/or low sodium levels in the blood. Use cautiously with diuretics and anti-inflammatories. The elderly should also use nettle cautiously because nettle may drastically reduce blood pressure. Avoid if pregnant because in one animal study, nettle caused uterine contractions. Avoid if breastfeeding due to insufficient evidence of safety.
: A homeopathic formulation containing an extract of witch hazel and tinctures of other botanicals was studied for its effects in relieving redness and itching associated with mosquito bites. According to study results, the formulation did not provide effective relief from mosquito bite symptoms. However, because information about the strength or concentration of the witch hazel extract used was not available, and witch hazel was not evaluated alone, conclusions about the effects of witch hazel on symptoms of insect bites cannot be made. Additional research is needed in this area.
Avoid if allergic or sensitive to witch hazel. Avoid if pregnant or breastfeeding. Use cautiously in people with liver or kidney disorders, diabetes, and in children.
Fair negative scientific evidence
: A comparative controlled trial did not find a clinically or statistically significant difference between fire ant bites treated with papain or placebo.
Use cautiously in patients with bleeding disorders or taking anticoagulants or antiplatelets. Use cautiously with radiation therapy or in patients being treated for prostatitis. Avoid in patients with gastroesophageal reflux disease or in patients using immunosuppressive therapy. Avoid in patients allergic or sensitive to papain.
Traditional or theoretical uses lacking sufficient evidence
Apple cider vinegar
: Apple cider vinegar has been used traditionally as a topical treatment for insect stings, including bee stings. Scientific evidence supporting the use of apple cider vinegar for insect bites is currently lacking.
Apple cider vinegar is likely safe when taken by mouth as food flavoring. Use caution if allergic or hypersensitive to apple cider vinegar or any of its ingredients (like apples and pectin). Use caution with a history of low potassium levels, diabetes or osteoporosis. Avoid if pregnant or breastfeeding.
: Based on anecdotal evidence, dried chamomile flowers have been added to bath water as a topical treatment for insect bites. High quality clinical study is needed in this area.
Avoid if allergic to chamomile. Anaphylaxis, throat swelling, skin allergic reactions and shortness of breath have been reported. Chamomile eyewash can cause allergic conjunctivitis (pinkeye). Stop use two weeks before surgery/dental/diagnostic procedures with bleeding risk, and do not use immediately after these procedures. Use cautiously if driving or operating machinery. Avoid if pregnant or breastfeeding.
Individuals with a history of anaphylaxis should carry an autoinjectable epinephrine device (known as an EpiPen©) with them at all times.
To avoid stinging insects, it is important to learn what they look like and where they live.
Avoid wearing sandals or walking barefoot in the grass.
Never swat at the insect.
Do not drink from open beverage cans if outside. Stinging insects are attracted to sweet beverages and may crawl inside.
Avoid wearing bright-colored clothing because stinging insects are attracted to vibrant colors.
- American Academy of Allergy Asthma & Immunology. www.aaaai.org. Accessed April 6, 2009.
- Medem: Medical Library. Insect Stings. American College of Allergy, Asthma and Immunology. View Article.
- National Institute of Allergy and Infectious Diseases. www3.niaid.nih.gov. Accessed April 6, 2009.
- Nemours Foundation. Insect Stings and Bites. View Article.
- Moffitt JE, Golden DB, Reisman RE, et al. Stinging insect hypersensitivity: a practice parameter update. J Allergy Clin Immunol. 2004 Oct;114(4):869-86. View Abstract.
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