Insect repellent is a staple of pharmacy summer sales, but navigating the range of active ingredients, concentrations and formulations can be confusing for both customers and staff. With tick-borne Lyme disease cases rising in the UK and international travel exposing holidaymakers to mosquito-borne diseases, evidence-based repellent advice is a genuine public health contribution from community pharmacy.
The Three Evidence-Based Active Ingredients
Three repellent active ingredients have robust evidence for efficacy against both mosquitoes and ticks, according to UKHSA and TravelHealthPro guidance:
1. DEET (N,N-diethyl-meta-toluamide)
DEET has been the gold standard insect repellent since the 1950s and remains the benchmark against which all other repellents are measured.
| Concentration | Protection duration | Best for |
|---|---|---|
| 20% | 3–4 hours | UK garden use, moderate outdoor activity |
| 30–50% | 6–8 hours | Hiking, camping, evening outdoor dining |
| 50% | 8–12 hours | Tropical travel, high-risk malaria areas |
Key points:
- Higher concentrations provide longer protection, not stronger protection — 50% lasts longer but is not "more repellent" per hour than 20%
- Effective against mosquitoes, ticks, midges, horseflies and sandflies
- Can damage some synthetic fabrics, plastics and watch faces
- Safe in pregnancy at concentrations up to 50%, according to UKHSA and TravelHealthPro
- Safe for children aged 2 months and over (avoid hands and face in young children)
Common UK brands: Jungle Formula Maximum (50% DEET), Lifesystems Expedition (50%), Sawyer Ultra 30 (30%)
2. Picaridin (icaridin / KBR 3023)
Picaridin is a synthetic repellent developed by Bayer in the 1990s and increasingly favoured for family use due to its favourable cosmetic profile.
| Concentration | Protection duration | Best for |
|---|---|---|
| 20% | 5–8 hours | Most outdoor activities, travel |
Key points:
- Comparable efficacy to DEET at similar concentrations
- Does not damage plastics, synthetic fabrics or sunglasses
- Feels less oily and has minimal odour compared to DEET
- Safe in pregnancy and for children aged 2 months and over
- Less evidence than DEET for tick repellency specifically, though still effective
Common UK brands: Smidge (20% picaridin), Lifesystems Midge & Tick (20%)
3. PMD (p-menthane-3,8-diol) / Citriodiol
PMD is derived from lemon eucalyptus oil and is the most effective plant-based repellent with formal regulatory approval.
| Concentration | Protection duration | Best for |
|---|---|---|
| 20–30% | 4–6 hours | UK outdoor use, customers wanting "natural" options |
Key points:
- The only botanical repellent recommended by UKHSA
- Effective against mosquitoes; tick evidence is weaker than DEET or picaridin
- Not suitable for children under 3 years (risk of skin sensitisation)
- "Lemon eucalyptus oil" on its own (without the PMD extraction process) is NOT equivalent and provides minimal protection
Common UK brands: Mosi-guard Natural (30% PMD), Care Plus Anti-Insect Natural (30%)
What Does NOT Work
Pharmacists should be prepared to steer customers away from products with no meaningful evidence of efficacy:
- Citronella candles and wristbands — no proven repellent effect beyond arm's length
- Electronic ultrasonic repellers — no credible evidence of efficacy
- Vitamin B1 (thiamine) supplements — a persistent myth with no supporting data
- Garlic consumption — no effect on mosquito attraction
- Tea tree oil, lavender oil, neem oil — variable and very short-lived activity, not recommended by any public health authority for disease prevention
Application Advice
Correct application significantly affects repellent performance:
- Apply to all exposed skin — mosquitoes will bite any unprotected area
- Apply sunscreen first, repellent second (wait 15–20 minutes between them). The repellent layer must be on top to work
- Reapply after swimming or heavy sweating — water removes the active ingredient
- Do not spray directly onto the face — spray onto hands first, then apply to face, avoiding eyes and mouth
- For clothing treatment, permethrin spray (e.g. Lifesystems EX4 Permethrin Spray) provides tick protection on trousers and socks that survives several washes — this is especially useful for walkers in tick-endemic areas
Children and Repellent Safety
| Age | DEET | Picaridin | PMD |
|---|---|---|---|
| Under 2 months | Not recommended | Not recommended | Not recommended |
| 2 months – 3 years | Up to 50% (apply sparingly) | Up to 20% | Not recommended |
| 3 years and over | Up to 50% | Up to 20% | Up to 30% |
For young children, apply repellent to the parent's hands first, then apply to the child's skin — avoiding hands (which go in mouths), eyes and any broken or irritated skin.
Pharmacy Stock Recommendations
For a well-rounded repellent display:
- DEET 50% — for travellers, serious hikers and tick-endemic areas
- Picaridin 20% — for family outdoor use and customers who dislike DEET's feel
- PMD 30% — for customers who prefer plant-derived products (aged 3+)
- Permethrin clothing spray — for tick protection on outdoor clothing
- Hydrocortisone 1% cream and antihistamines — for customers already bitten
For more information on pharmacy services and health advice in your area, visit PharmSee's pharmacy finder or explore local pharmacy data.
Sources: UKHSA Insect Bite Avoidance Guidance, TravelHealthPro, NHS England, WHO Pesticide Evaluation Scheme (WHOPES).