• Anaphylaxis can occur after an insect sting (usually within minutes), particularly from a bee or wasp, and requires urgent action.
• Anaphylaxis after an insect bite is rare.
• Multiple bee or wasp stings may cause systemic toxicity which requires urgent action as this can be fatal, particularly in children.
• Late-onset reactions to stings can occur (after several hours), which present as urticarial reactions, or serum sickness-like reactions with urticaria, joint swelling and arthralgia.

• If a severe systemic reaction occurs, such as wheezing or other signs of respiratory distress, or hypotension:
• Treat urgently as for anaphylaxis and admit to hospital.
• If there are symptoms of systemic toxicity that suggest impending anaphylaxis (e.g. abdominal pain, vomiting, rhinitis and conjunctivitis, or a sense of impending doom):
• Treat as for anaphylaxis and admit to hospital.
• If generalized urticaria occurs, but the person is otherwise well:
• Give an oral antihistamine and an oral corticosteroid.
• Offer a non-sedating antihistamine to control daytime symptoms.
• Consider giving an additional sedating antihistamine at night if the itch is interfering with sleep.
• In adults, give prednisolone 40 mg once a day, and in children give 1–2 mg/kg body weight once a day.
• Continue prednisolone for 3–5 days, depending on the severity of the reaction.
• Advise the person to seek urgent medical help if the rash worsens, swelling develops which involves the mouth or throat, or wheeze or breathing difficulty occurs.

In depth

• Admit all patients with anaphylaxis, after immediate emergency management.
• If mild symptoms appear to be worsening then admission may be required for observation (uncommon).
• The decision to admit will depend upon on the type of reaction, social circumstances, and access to local medical facilities. Exercise clinical judgement in these circumstances.
• Consider referral to an allergy clinic if an insect sting or bite has caused generalized symptoms.
• The Anaphylaxis Campaign recommends referral to an allergy clinic if there is a large local skin reaction, with redness and swelling over 10 cm in diameter. However clinicians should check the referral policy of their local allergy clinic as this may vary.
• Seek specialist advice from an allergy clinic or immunologist regarding local recommendations for interim management of anyone waiting to be seen by the allergy clinic.

In depth

• If symptoms of generalized urticaria are mild follow-up is generally not necessary.
• Advise review if they have worsening urticaria.
• Advise urgent medical review if symptoms of systemic toxicity develop.
• Anyone who has had anaphylaxis; check that an appointment has been made for referral to an allergy clinic.