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.
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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.
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.