Bee Venom Allergy

Bee venom allergy is an IgE-mediated allergy to honeybee (Apis mellifera) venom. It commonly affects beekeepers and their families and causes severe reactions.

Pathophysiology. The principal allergens are phospholipase A2 (Api m 1), hyaluronidase (Api m 2), and Api m 3 and Api m 10, with cross-reactive carbohydrates causing false positive results in wasp sensitised patients. Bumblebee venom is cross-reactive with honeybee venom.

Unlike wasps, bees leave a barbed sting with a venom sac that continues to inject venom for up to a minute, so prompt removal limits the dose.

Beekeepers are exposed to repeated stings, which may lead to either sensitisation or natural tolerance.

• Large local swelling, pain and redness around the sting
• Generalised urticaria, flushing and angio oedema
• Wheeze, stridor, hypotension and collapse
• Gastrointestinal symptoms: vomiting, cramps
• Reactions within minutes of a sting
• Occupational reactions in beekeepers and in people exposed to hive products (propolis, royal jelly) through different mechanisms

• History: the insect (bees die after stinging and leave a stinger), circumstances, time to onset and features.
• Skin prick and intradermal test with honeybee venom (and wasp venom for comparison), and specific IgE to honeybee venom and Api m 1 and Api m 10: Api m 1 positivity indicates genuine honeybee sensitisation, and Api m 10 is helpful in defining the primary sensitiser. Cross-reactive carbohydrate determinants cause double positivity.
• Baseline tryptase: raised values suggest mast cell disease.
• Basophil activation test where available in double positive patients.

Differential diagnosis.

• Wasp, hornet or bumblebee venom allergy
• Large local reaction without systemic risk
• Idiopathic anaphylaxis
• Systemic mastocytosis
• Reaction to propolis or royal jelly
• Cellulitis at the sting site

• Immediate care after a sting: scrape the stinger out immediately with a fingernail or card (do not squeeze), cool the site, and give an oral antihistamine for local symptoms: cetirizine 10 mg in adults (children 1 to 5 years 2.5 mg twice daily; 6 to 11 years 5 mg twice daily).
• Anaphylaxis: adrenaline 0.5 mg intramuscularly (children 0.01 mg/kg, maximum 0.5 mg) into the anterolateral thigh, repeated after 5 minutes if no improvement, plus oxygen and intravenous fluids, and observation for at least 6 hours.
• Adrenaline auto injector: 150 microgram for 7.5 to 25 kg, 300 microgram for 25 to 50 kg, 500 microgram for over 50 kg, with a written action plan and training.
• Honeybee venom immunotherapy for systemic reactions: build up then maintenance of 100 microgram of venom every 4 weeks (200 microgram if reactions continue), for 3 to 5 years, and often lifelong in beekeepers and in mastocytosis. It prevents systemic reaction in more than 90% of treated patients.
• Sting avoidance: avoid hives and flowering plants, protective clothing, veils and gloves, and smoke control.
• Beekeepers: continue immunotherapy while working, and keep an auto injector at the hives.
• Review drugs: beta blockers and angiotensin converting enzyme inhibitors.

Special groups.

• Beekeepers: with immunotherapy, follow up sting challenge is considered to confirm protection.
• Patients with mastocytosis: lifelong immunotherapy.

Monitoring. Review every 6 months during build up and yearly in maintenance. Check auto injector dose and expiry. Baseline tryptase yearly.

Referral and escalation. Refer to allergy for any systemic reaction to a bee sting, and for all beekeepers with reactions. Emergency for anaphylaxis.