Conditions · Emergency medicine and toxicology
Hymenoptera stings (bees, wasps, ants) !
Stings by bees, wasps or fire ants. Most cause local pain and swelling; some trigger anaphylaxis, and hundreds of stings can poison the whole body.
Updated 2026-11-01
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Why it happens
- Histamine, serotonin, bradykinin and the plasma protein cascades
- Shock: types, stages and the organs it damages
- Innate and adaptive immunity: overview
What it is
Reactions to the venom of bees, wasps, hornets and ants. They range from a painful local wheal to large local reactions, allergic anaphylaxis (the main cause of death) and, with mass attacks such as those of Africanized bees, direct toxic envenomation that breaks down red cells and muscle and injures the kidneys.
Who gets it
Stings are very common worldwide. Africanized honeybees spread through Latin America from the 1950s and reached Colombia in the 1980s; they defend the hive aggressively and in swarms, so mass attacks on farm workers, children and older adults occur. Fire ants are common in warm lowlands. Systemic allergic reactions occur in a small percentage of adults and are a leading cause of anaphylaxis outside hospital.
Causes
- Bees: barbed stinger left in the skin with its venom sac; venom with melittin, phospholipase A2 and hyaluronidase
- Wasps, hornets and yellow jackets: smooth stinger allowing repeated stings
- Fire ants: bite to anchor and then sting repeatedly in a circle, leaving sterile pustules
- Mass attack: hundreds of stings from Africanized bees
Risk factors
- Previous systemic reaction to a sting
- Beekeepers, farm and outdoor workers
- Mastocytosis or high baseline serum tryptase
- Older age, heart disease and use of beta-blockers (more severe anaphylaxis, harder to treat)
- Children and older adults in mass attacks
Pathophysiology
Venom peptides and enzymes cause local pain, inflammation and swelling. In sensitised people, venom-specific IgE on mast cells triggers degranulation with histamine and other mediators, causing vasodilation, capillary leak, bronchospasm and laryngeal oedema (type I hypersensitivity). In mass envenomation, large amounts of melittin and phospholipase A2 directly destroy red cells and muscle, releasing haemoglobin and myoglobin that injure the kidney tubules.
Classification
- Local reaction: pain, redness and swelling at the sting
- Large local reaction: swelling over 10 cm lasting more than 24 hours, next to the sting
- Systemic allergic reaction: from generalised skin signs to anaphylaxis
- Toxic reaction from multiple stings: haemolysis, rhabdomyolysis, kidney and liver injury
- Unusual late reactions: serum sickness, vasculitis, neurological syndromes
Symptoms and signs
- Immediate sharp pain, a red wheal and swelling at the sting site
- Generalised hives, itching and flushing
- Swelling of the lips, tongue or throat, hoarseness and difficulty swallowing
- Wheezing, shortness of breath, dizziness and fainting
- Nausea, vomiting, cramps and diarrhoea
- After many stings: dark urine, muscle pain, vomiting and confusion hours later
Diagnosis
- Clinical
- History of the insect and number of stings, timing of symptoms and examination of skin, airway, breathing and circulation. Anaphylaxis is a clinical diagnosis and treatment is never delayed for tests.
- Tests
- After a mass attack: blood count, creatine kinase, urinalysis, creatinine, electrolytes, liver enzymes and coagulation. Serum tryptase in suspected anaphylaxis. Later, skin tests or venom-specific IgE in people with systemic reactions to plan immunotherapy.
- Imaging
- Not routinely needed.
Differential diagnosis
- Cellulitis (a large local reaction is often mistaken for infection)
- Hereditary or drug-induced angioedema
- Vasovagal syncope or panic attack
- Asthma attack from another trigger
- Other envenomations (scorpion, spider)
Goal of treatment
Recognise and treat anaphylaxis at once, relieve local symptoms, protect the kidneys after a mass attack and prevent future reactions.
Treatment
- Acute
- Remove the bee stinger quickly by any means. For anaphylaxis: intramuscular adrenaline (epinephrine) in the lateral thigh without delay, lying position with legs raised, oxygen, intravenous fluids, and airway management; repeat adrenaline if there is no response.
- Medical
- Antihistamines and corticosteroids as adjuncts (never instead of adrenaline); inhaled bronchodilators for wheeze; cold compresses and analgesics for local reactions. After mass envenomation, generous intravenous fluids to protect the kidneys and treatment of hyperkalaemia; dialysis if kidney failure develops.
- Follow-up
- Observation for hours after anaphylaxis because of possible biphasic reactions; urine output, urine colour and kidney function after many stings.
- Lifestyle
- Adrenaline auto-injector and written action plan for people with prior systemic reactions; referral to allergy for venom immunotherapy, which greatly reduces future risk.
Complications
- Anaphylactic shock and airway obstruction
- Myocardial ischaemia triggered by the allergic reaction (Kounis syndrome)
- Rhabdomyolysis and haemolysis with acute kidney injury
- Liver injury and coagulopathy after mass attacks
- Secondary infection of scratched stings
Prognosis
Local reactions settle in hours to days. Anaphylaxis is usually reversible when adrenaline is given promptly; deaths happen mostly when it is delayed. Mass envenomation can be fatal, especially in children and older adults, mainly from kidney failure.
Prevention
- Avoid disturbing hives and nests; seek trained removal
- Wear shoes, long sleeves and avoid strong scents outdoors
- When attacked by a swarm, run to a closed shelter and cover the face; do not jump into water
- Carry an adrenaline auto-injector and consider venom immunotherapy after a systemic reaction
Test yourself
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What is the first-line drug for anaphylaxis after a bee sting, and by which route?
Adrenaline (epinephrine) intramuscularly in the lateral thigh, given immediately; antihistamines and corticosteroids are only adjuncts.
Which treatment reduces the risk of future systemic reactions to venom?
Venom immunotherapy, offered to people who have had a systemic reaction and have proven venom-specific IgE.
Why can a mass attack by Africanized bees cause kidney failure even without allergy?
The large dose of venom (melittin, phospholipase A2) destroys red cells and muscle; haemoglobin and myoglobin damage the renal tubules.
Why are people observed for hours after anaphylaxis has resolved?
Because symptoms can return hours later without a new exposure (biphasic reaction).
Related conditions
- Anaphylaxis
- Urticaria and angioedema
- Rhabdomyolysis
- Acute kidney injury
- Asthma
- Myocardial Infarction (Heart Attack)
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Bee, wasp, hornet, or yellow jacket sting (MedlinePlus, US National Library of Medicine, 2026); Insect bites and stings (MedlinePlus, US National Library of Medicine, 2026).
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