DEET (N,N-diethyl-meta-toluamide) is the most widely used and most effective insect repellent available for consumer use — it is the recommended active ingredient for malaria and dengue prevention in tropical travel destinations by WHO, the NHS, and travel medicine authorities worldwide. DEET works by blocking insect olfactory receptors that detect human-produced attractant compounds. At concentrations of 20–50%, DEET provides reliable protection against mosquitoes, ticks, and other biting insects for 4–8 hours. The safety paradox is that DEET is both genuinely effective at a public health-significant task (preventing malaria and other vector-borne diseases) and a chemical that is significantly absorbed through human skin, detected in human blood and urine after topical application, and associated with neurological effects in animals at high doses. For travellers to malaria-endemic areas, the benefit-risk calculation favours DEET use. For domestic UK use against midges and mosquitoes, lower-concentration alternatives with better safety profiles are worth considering.
Where it's found
Consumer insect repellent sprays, lotions, and wipes sold for travel use — brands including Jungle Formula (30–50% DEET), Repel, Off!, and Ultrathon. Prescription-level high-concentration DEET products (50%) recommended for high-risk malaria areas by travel clinics. Lower-concentration (10–20%) DEET products for casual domestic use. DEET products are sold in pharmacies, travel clinics, and outdoor retailers. Applications in holiday destinations may also include DEET-containing products distributed at resorts in malaria-endemic tourist areas.
Routes of exposure
Dermal absorption — DEET is well absorbed through human skin: studies find that 5–17% of an applied dose enters the bloodstream within 6 hours. Repeated application multiple times daily over a fortnight's holiday results in significant cumulative systemic exposure. DEET is detected in blood within 1–2 hours of skin application and cleared primarily via urine within 12 hours. Inhalation of DEET spray aerosol during application. Oral ingestion — particularly in children who may lick DEET from treated skin or hands.
Health concerns
DEET is a cholinesterase inhibitor in insects, but its mechanism in humans is less clearly defined — human neurological toxicity from DEET has been documented primarily in cases of excessive use or accidental ingestion. Case reports describe seizures, encephalopathy, and cardiovascular effects from massive DEET overdose. At recommended travel use concentrations, epidemiological evidence does not support neurological harm in adults. DEET dissolves plastics and synthetic fabrics — it damages watch crystals, sunglasses frames, and synthetic clothing on contact, indicating its significant chemical potency. Combined use with sunscreen reduces DEET skin absorption (sunscreen acts as a physical barrier), but sunscreen applied over DEET reduces sunscreen SPF and requires more frequent reapplication.
Evidence
DEET efficacy as an insect repellent is established — it is the WHO-recommended standard for malaria-endemic area protection. Dermal absorption of DEET and its detection in human blood and urine is established analytically. Neurological toxicity from DEET overexposure and ingestion is established from case reports. The absence of neurological harm at recommended doses in healthy adults is supported by large-scale military and traveller use without documented adverse neurological outcomes at recommended concentrations. DEET use in pregnancy and in children under 2 requires specific precaution.
Who's most at risk
Young children in whom DEET concentration limits apply — NHS guidelines recommend maximum 50% DEET for children over 2 years but with minimised application. Infants under 2 months where DEET is not recommended. Pregnant women — DEET crosses the placenta; cautious use at lowest effective concentrations is recommended in malaria-endemic areas where the risk-benefit still favours use. People who apply DEET repeatedly to large body surface areas over extended periods.
Regulatory status
RegulationDEET-containing insect repellents are classified as biocidal products in the UK under the Biocidal Products Regulation — they require authorisation. DEET products must carry child safety warnings and concentration labelling. NHS and Travel Health Pro provide evidence-based guidance on DEET concentrations by risk zone. DEET is not restricted from adult use; child use is guided by concentration recommendations (20% for most travel situations) rather than prohibition.
How to reduce your exposure
Apply DEET to clothing rather than directly to skin where possible — DEET on fabric is highly effective at repelling insects while avoiding dermal absorption. Use the minimum effective concentration: 20–30% DEET provides excellent protection for most holiday destinations; 50% is warranted for high-malaria-risk areas. Apply sunscreen first, allow to absorb, then apply DEET over the top — this sequence provides both sun and insect protection while reducing DEET absorption. Consider icaridin (picaridin) as a DEET alternative: equally effective, with significantly less skin absorption and no plastic-damaging effects. For UK domestic use against midges, Saltidin (icaridin) or citriodiol are lower-risk alternatives.
The nutrition connection
DEET's neurological effects at high doses involve cholinesterase inhibition and possible GABA receptor interaction — B vitamin nutrition (particularly B1, choline) and GABA-supporting magnesium are relevant. However, at recommended travel doses, the primary nutritional relevance is supporting skin barrier function (which reduces DEET absorption) and hepatic detoxification of absorbed DEET (CYP2B6-mediated in the liver). Adequate zinc and essential fatty acids for skin barrier integrity, and cruciferous vegetables for liver CYP enzyme support, are the main dietary strategies. Adequate hydration supports urinary DEET metabolite excretion.