Pharmacy First: Infected Insect Bites

About this service

Infected insect bites and stings are one of the seven conditions covered by the NHS Pharmacy First service. The pathway applies to children aged 1 year and over and adults, and covers bites and stings from both six-legged insects (such as mosquitoes, gnats, and flies) and eight-legged arthropods (such as spiders, mites, and ticks).

The critical clinical distinction is between normal inflammatory reaction to a bite (which does not require antibiotics and should be managed with self-care) and a true soft tissue infection (which may qualify for antibiotic treatment under the PGD). Antibiotics are only appropriate when there is clear evidence of infection that has been present or worsening for at least 48 hours after the initial bite, with specific clinical signs present.

Tick bites are excluded from this pathway entirely due to the risk of Lyme disease. Erythema migrans (the characteristic expanding rash) should always be recognised and referred, and pharmacists should be aware that on darker skin tones it may appear more like a bruise than a classic bullseye pattern.

Who to offer the service to

Include

• Aged 1 year and over
• Bite or sting from an insect or arthropod (including spiders, mites, and ticks are in scope for assessment, but see tick exclusion below)
• Clear evidence of infection present or worsening at least 48 hours after the initial bite or sting (see inclusion criteria table below)
• NHS eligibility requirements apply

Exclude

• Under 1 year old: outside the Pharmacy First pathway. Refer to GP.
• Pregnancy under 16: excluded. For pregnant individuals aged 16 and over, a separate erythromycin PGD (4c) applies.
• No clear evidence of infection: initial inflammation around a fresh bite should be managed with self-care (see below). Do not supply antibiotics for a normal inflammatory bite reaction.
• Tick bite (any tick bite where the tick is still present, or where the presentation is consistent with a tick bite): refer to GP due to risk of Lyme disease
• Erythema migrans (expanding bullseye rash, or bruise-like marking on darker skin tones): refer to GP urgently. Do not supply antibiotics under this PGD.
• Bite or sting that occurred while travelling outside the UK with concern about insect-borne disease (e.g. malaria, tick-borne encephalitis): refer to GP
• Bite or sting caused by an unusual or exotic insect: refer to GP
• Human bite or animal bite or scratch: refer to GP
• Bite or sting in the mouth, throat, or around the eyes: refer to A&E urgently (airway or vision at risk)
• Suspected anaphylaxis or angio-oedema: refer to A&E urgently
• Previous systemic allergic reaction to the same type of bite or sting: refer to A&E urgently
• Severely immunocompromised: refer to GP same day
• Known comorbidity that may delay resolution: peripheral arterial disease, chronic venous insufficiency, lymphoedema, or morbid obesity: refer to GP
• Known liver disease or previous flucloxacillin-associated jaundice or liver dysfunction: excluded from flucloxacillin. Refer to GP.
• Known MRSA colonisation or infection: refer to GP
• Severe pain out of proportion to the wound (possible toxin-producing bacteria): refer to GP urgently
• Significant collection of fluid or pus requiring drainage: refer to GP
• Numbness or tingling of the affected area: refer to GP
• Puncture wound contaminated with fresh water, sea water, soil, or manure: refer (may need alternative antibiotics or tetanus prophylaxis)
• Systemically unwell: refer to GP or A&E depending on severity
• Sepsis suspected: call 999

How to deliver the service

1. Screen for red flags and urgent exclusions first Before assessing for infection, check for features requiring immediate referral. Anaphylaxis or angio-oedema: A&E immediately. Bite or sting in the mouth, throat, or around the eyes: A&E immediately. Erythema migrans: refer to GP urgently (do not treat under this PGD). Systemically very unwell or sepsis: call 999 or refer to A&E. Previous systemic allergic reaction to the same bite type: A&E.
2. Check for tick bites and Lyme disease risk All tick bites are excluded from this pathway due to the risk of Lyme disease, regardless of whether infection signs are present. Erythema migrans is the hallmark rash of early Lyme disease: an expanding erythematous ring, often described as a bullseye pattern, appearing days to weeks after a tick bite. On darker skin tones it may appear more as an expanding bruise-like marking than a red ring. If suspected, refer to GP urgently rather than supplying flucloxacillin, which is not appropriate for Lyme disease.
3. Confirm the bite is at least 48 hours old and check exclusions Ask when the bite or sting occurred. Bites presenting within 48 hours with redness and swelling may simply reflect normal inflammation, not infection. If the bite is less than 48 hours old and there is no spreading or discharge, advise self-care and ask the patient to return if it is not improving after a further 48 hours. Check for liver disease, previous flucloxacillin jaundice, MRSA, penicillin allergy, and the other exclusions listed above.
4. Apply the infection criteria Confirm that 3 or more infection signs are present (redness, pain or tenderness, swelling, warmth) AND that there is at least one spreading feature (redness or swelling is spreading beyond the bite site, or pustular discharge is present). Draw a line around the border of the erythema at the time of assessment and document its extent in the clinical record.
5. Select the antibiotic and check interactions Flucloxacillin is first line. Before supplying, check for methotrexate, probenecid, and voriconazole (must not supply under this PGD). Check for warfarin use (INR monitoring advised). For penicillin allergy, use clarithromycin dosed by weight using BNF for Children. For pregnant individuals aged 16 and over, apply the erythromycin PGD 4c. Counsel on taking flucloxacillin on an empty stomach: 1 hour before food or 2 hours after food.
6. Counsel and safety net Advise: avoid scratching, keep fingernails short and clean, keep hands clean when touching the area. Skin redness and itch may take up to 10 days to fully resolve even after antibiotics. Safety netting: return immediately if the infection spreads further, if new symptoms develop (fever, severe pain, swelling of face or throat), or if there is no improvement after completing the course. Advise seeking urgent help if signs of sepsis develop. Document the erythema border drawn at assessment.

Assessment outcome: what to do

Infection Criteria: All of the Following Must Apply

Infection must be present or worsening at least 48 hours after the initial bite or sting. Initial redness and swelling in the first 48 hours is a normal inflammatory response and does not qualify for antibiotic treatment.

Flucloxacillin Doses (four times daily, on empty stomach, for 5 days)

Take 1 hour before food or 2 hours after food. For penicillin allergy use clarithromycin by weight (BNFc for all ages). Pregnant individuals aged 16 and over: follow erythromycin PGD 4c.

Self-Care for Non-Infected or Early Bites

Where infection criteria are not met, or the bite is less than 48 hours old, advise self-care and ask the patient to monitor for spreading.

Recording and submission

• Complete the consultation record contemporaneously on PharmOutcomes.
• Key information to record:
  • Patient name, date of birth, NHS number
  • Duration since bite (at least 48 hours confirmed)
  • Site of bite and description of the area including extent of erythema (draw border at assessment)
  • Infection signs present: which of the four were found and how many
  • Spreading feature confirmed: spreading erythema or pustular discharge
  • Tick bite and Lyme disease risk assessed and excluded
  • Exclusions checked (liver disease, MRSA, co-morbidities, travel history, bite type)
  • Antibiotic supplied: name, strength, dose, frequency, duration, quantity, batch number, expiry date
  • Penicillin allergy status confirmed
  • Drug interactions checked
  • Self-care advice and safety netting given
  • Referral made if applicable

Key takeaways

• Infection must be present or worsening at least 48 hours after the bite, with 3 or more infection signs AND spreading redness or pustular discharge. Bites under 48 hours with redness alone are a normal inflammatory reaction: advise self-care.
• All tick bites are excluded from this pathway due to Lyme disease risk. Always check for erythema migrans, which may look like a bruise on darker skin tones, and refer to GP urgently if suspected.
• Flucloxacillin is four times daily on an empty stomach for 5 days. Draw a border around the erythema at assessment and document its extent.

Download the checklist