• Scenario: Small local reactions: covers the management of someone with a small local reaction to an insect bite or sting.
• Scenario: Large local reactions: covers the management of someone with a large local reaction to an insect bite or sting.
• Scenario: Systemic reactions: covers the management of someone who has had a systemic reaction to an insect bite or sting. It does not discuss the management of anaphylaxis. See the CKS topic on Angio-oedema and anaphylaxis for a detailed discussion on how to manage anaphylaxis.
• Scenario: Infection: covers the management of someone with an infected bite or sting.

• Small local reactions to insect bites or stings present with localized pain, swelling, and erythema at the site of the bite or sting. Most can be managed symptomatically.

• If a person has been stung and the stinger is still in place:
• Remove it as soon as possible by flicking or scraping with a fingernail, piece of card, or knife blade.
• Never squeeze the stinger or use tweezers, as this will cause more venom to go into the skin.
• Remove ticks as soon as possible.
• Wash the area of the bite or sting with soap and water.
• Apply ice to reduce swelling, if present.
• Do not scratch, as this will cause the site to swell and itch more, and increase the chance of infection.
• If there are signs of a severe allergic reaction (generalized symptoms, breathing difficulties, and/or hypotension) seek urgent medical help.
• Bites from fleas, mites, and bedbugs may be due to an infestation. The source of the infestation should be confirmed and then eliminated.

In depth

• Treat local pain and oedema with cold compresses and oral analgesics (e.g. paracetamol or ibuprofen).
• Treat local itching with topical crotamiton. Alternatively, consider using a mild potency topical corticosteroid (e.g. hydrocortisone 1%).
• Consider an oral sedating antihistamine at night if the itch is interfering with sleep.

In depth

• Follow-up or referral is usually not necessary for anyone with a small local reaction to an insect bite or sting.
• Admission may be required for observation when mild symptoms progress to a severe reaction (uncommon).
• The decision to admit will depend upon the type of reaction, social circumstances, and access to local medical facilities. Exercise clinical judgement in these circumstances.

• Large local reactions present with severe pain, and oedema that extends beyond the site of the sting or bite. Most can be managed symptomatically.
• Late-onset reactions can occur (after several hours), which present as urticarial reactions or serum sickness-like reactions with urticaria, joint swelling, and arthralgia.

• Treat pain with an oral analgesic (e.g. paracetamol or ibuprofen).
• Treat large local allergic reactions with a short course of an oral antihistamine.
• Offer a non-sedating antihistamine to control daytime symptoms.
• Consider giving an additional sedating antihistamine at night if the itch is interfering with sleep.
• Consider using a short course of an oral steroid (e.g. prednisolone for 3–5 days) if local swelling is severe.
• If the airway is affected, treat urgently as anaphylaxis — see the CKS topic on Angio-oedema and anaphylaxis for more information.

In depth

• Admission may be required for observation when mild symptoms progress to a severe reaction (uncommon).
• The decision to admit will depend upon the type of reaction, social circumstances, and access to local medical facilities. Exercise clinical judgement in these circumstances.
• 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.

• If a person has a local reaction to an insect bite or sting:
• Follow-up is not usually required unless symptoms are worsening.
• If the person presents with a severe local reaction, consider reviewing within 2–3 days.
• Advise urgent medical review if symptoms of systemic toxicity develop.
• Remember to consider indications for referral to an allergy clinic.

• 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.

• Secondary bacterial infection may occur as a result of scratching or may be introduced at the time of the bite or sting.

• A secondary infection may appear as impetigo, cellulitis, or lymphangitis.
• Signs that suggest a secondary infection include:
• The presence of pus.
• Increasing erythema, oedema, or tenderness beyond the anticipated pattern of response.
• Regional lymphadenopathy — this can also occur in the absence of infection, as a response to the inflammatory reaction produced by a bite.
• Lymphangitis, which is the most reliable sign and suggests streptococcal involvement.

• Treat empirically with oral antibiotics for 7 days:
• Oral flucloxacillin is recommended for empirical treatment of staphylococcal and streptococcal skin infections.
• Oral erythromycin (or clarithromycin if erythromycin is not tolerated) is an alternative for people with penicillin-allergy.

In depth

• Seek specialist advice regarding further management.