DEET (N,N-diethyl-meta-toluamide) is the most widely used active ingredient in insect repellents worldwide, effective against mosquitoes, ticks, midges, and other biting insects. It has been used since the 1940s. DEET is generally considered safe when used as directed in adults, but concerns persist about its neurotoxic potential, particularly in young children, and its ecological impact on aquatic invertebrates. It is also a potent plasticiser that damages polystyrene, lycra, and many synthetic fabrics — a warning label characteristic that has raised questions about its dermal safety.
Where it's found
Personal insect repellent sprays, lotions, and wristbands for use in gardens, camping, hiking, and overseas travel. Holiday and travel products for malaria-endemic and arbovirus (dengue, Zika) risk areas. DEET-treated clothing for military and outdoor use. Some pet insect repellent products. Travel health kits and pharmacist-recommended malaria prevention products. Available in concentrations from 5% (for light use, children) to 98% (military grade, prolonged protection).
Routes of exposure
Dermal absorption through skin application is the primary route — DEET is readily absorbed through intact skin. Absorption is greater from damaged or broken skin and from application to mucous membranes. Absorption is higher under clothing and in hot, humid conditions. Inhalation during spray application — particularly from aerosol formulations — contributes to exposure. Inadvertent ingestion from hand-to-mouth contact, or from spray application near the mouth in children, occurs. In countries with significant mosquito-borne disease risk, the protective benefit against malaria, dengue, and other diseases substantially outweighs the risks from DEET exposure — the calculation is different in the UK where the disease risk is negligible.
Health concerns
DEET has a well-established safety record when used as directed in adults at recommended concentrations. However, it is neurotoxic in animals at high doses — causing tremor and behavioural effects through inhibition of acetylcholinesterase (the same mechanism as organophosphate insecticides, though less potently). Case reports of encephalopathy in young children from excessive or repeated application are documented, though rare. DEET penetrates the blood–brain barrier. Studies suggest DEET may impair cognitive function and act as a neurotoxin at higher exposures. Some research suggests DEET combined with permethrin has synergistic neurotoxic effects greater than either alone.
Evidence
The safety record for adults using DEET at recommended concentrations is generally reassuring from decades of use. The paediatric concern — encephalopathy cases in young children — is documented but rare. The neurotoxicity mechanism (AChE inhibition) is real but the clinical relevance at label concentrations in adults is debated. Some in vitro and animal studies suggest greater concern than the regulatory position. The combination with permethrin is a specific area of emerging concern based on animal data.
Who's most at risk
Children under 2 are most vulnerable — UK NHS guidance recommends against DEET use under 2. Children generally should use lower concentrations (20–30%) and have parents apply rather than self-apply. Pregnant women: DEET crosses the placenta — recommendations vary by country, with high-risk disease travel requiring the benefit to be weighed against risk. People with impaired skin barrier (eczema, skin conditions) absorb more DEET. Overuse or application to large skin areas increases systemic dose.
Regulatory status
RegulationDEET is a regulated biocide under EU BPR and UK equivalent regulations. UK NHS guidance recommends DEET concentration of 20–50% for general use; concentrations above 50% are not recommended for children. Products for children must carry appropriate age warnings. DEET is not recommended for infants under 2 months by CDC/NHS. EU and UK label requirements limit application instructions. DEET is listed as an emerging aquatic contaminant of concern.
How to reduce your exposure
Use DEET only when there is a genuine biting insect risk and when other repellents are insufficient. In the UK, for midge and mosquito protection in gardens and countryside, lower concentrations of DEET or plant-based alternatives (eucalyptus lemon oil, citriodiol/PMD — which the NHS considers acceptable for children over 2) may be sufficient. For high-risk malaria or arbovirus travel, DEET is the most effective option — use the lowest effective concentration. Apply to clothing rather than skin where possible. Avoid applying to children's hands (hand-to-mouth) and around the eyes and mouth. Do not apply to broken skin. Wash off when returning indoors.
The nutrition connection
DEET sits in the "necessary evil" category for travel health — in genuine malaria-endemic regions the disease risk vastly outweighs DEET risk, and its use is strongly recommended. In the UK, the risk–benefit calculation is different: biting insects here carry no significant disease risk, so the threshold for DEET use should be higher. Plant-based repellents and physical barriers (long sleeves, screens) are appropriate first choices for most UK outdoor activities. This connects to Nutriofia's broader principle: chemicals in products — including safety products — should be used proportionately to the genuine risk they address.