DEET vs Picaridin vs OLE vs IR3535

DEET — The Reference Standard

DEET (N,N-Diethyl-meta-toluamide) has been protecting people from mosquito bites since the US Army developed it in 1946. It is the most studied repellent on the planet, with EPA registration since 1957 and an active-ingredient safety dossier that includes decades of dermal-exposure data [1][9]. At concentrations of 20–30%, it provides 6–8 hours of reliable protection against virtually all biting mosquitoes, including the Anopheles species that transmit malaria [1][2].

Higher concentrations do not repel better — they just last longer. A 30% formulation is the sweet spot for most tropical travel; anything above 50% buys diminishing returns and a stronger smell. The downsides are real but manageable: DEET has a distinctive solvent odour, it can degrade plastics and certain synthetic fabrics, and many people find it greasy on the skin at high concentrations.

DEET is considered safe at recommended concentrations on adults and children aged two months and older [6][8]. The CDC and AAP both recommend it for pregnant women travelling to malaria-endemic destinations, where the benefit clearly outweighs the negligible risk [1][6]. Apply only to exposed skin (not under clothing), avoid eyes and mouth, and wash off when you come indoors.

Picaridin — The Modern Default

Picaridin (also called Icaridin or KBR 3023) was developed by Bayer in the 1990s and has been steadily gaining ground on DEET ever since. The 2020 review in Infectious Diseases in Clinical Practice and prior field studies (notably Frances et al. 2004 in the Journal of Medical Entomology) found that 20% Picaridin matches 20–25% DEET for both duration and efficacy against Aedes aegypti and Anopheles mosquitoes [2][5]. WHO has formally endorsed Picaridin for use in malaria-endemic areas, putting it in the same operational category as DEET for high-risk travel [3][7].

The practical advantages add up: Picaridin is near-odourless, does not damage plastics or fabrics, feels lighter on skin, and leaves no greasy residue. If you have ever had DEET melt a watch strap or stain a rain jacket, those problems disappear with Picaridin. It is also less likely to provoke skin irritation in sensitive users, which is part of why it is the easier sell to kids and reluctant family members.

For most travel — urban tropics, resorts, family trips, day-long hiking in malaria-free countries — Picaridin 20% is the better default. Below 15% the duration drops sharply, so make sure the product you grab is at the recommended concentration; many drugstore formulations are 5–10% and require more frequent reapplication.

Oil of Lemon Eucalyptus (OLE / PMD) — The Plant-Based Option

Oil of Lemon Eucalyptus is the only plant-based active recognised by the CDC and EPA as a meaningful repellent [4][9]. The compound that does the work is PMD (para-menthane-3,8-diol), a refined extract — not raw lemon eucalyptus essential oil, which has not been shown to repel reliably. At 30% PMD, OLE provides 2–4 hours of protection against most mosquito species, shorter than DEET or Picaridin but enough for an evening walk or a short hike in low-risk terrain [4].

OLE has a noticeable eucalyptus scent that many people prefer to the solvent edge of DEET. It is a reasonable choice for European city breaks, Mediterranean holidays, or anywhere mosquitoes are a nuisance rather than a disease vector. The single non-negotiable limit is age: OLE is not approved for children under three years old [4][6]. The CDC is explicit on this.

Do not confuse Oil of Lemon Eucalyptus (the registered repellent) with pure lemon eucalyptus essential oil. They are different products with very different evidence bases. If the label does not say "PMD" or "Oil of Lemon Eucalyptus" with an EPA registration number, it is essential oil — and there is no clinical evidence that essential oils repel mosquitoes reliably.

IR3535 — The European Favourite

IR3535 (ethyl butylacetylaminopropionate) was developed by Merck KGaA in the 1970s and has been a staple of European insect repellents for decades. Avon’s Skin So Soft Bug Guard line is the most familiar consumer brand using it, and Coleman, Sawyer, and various European brands sell IR3535 formulations alongside their DEET and Picaridin products. At 20% concentration, IR3535 provides roughly 4–6 hours of protection against most mosquito species [5].

The safety profile is excellent, which is why IR3535 shows up in many family-oriented and skincare-adjacent products — it is non-greasy, has a mild scent, and does not damage plastics aggressively (though it can mark certain synthetic fabrics). Its weak point is efficacy against Anopheles mosquitoes at high biting pressure; the 2020 IDCP review found it less effective than DEET or Picaridin against malaria-vector species [5]. So it is not the first choice for sub-Saharan Africa or PNG, but it is a sensible default for Mediterranean travel, European summer, and family use where Aedes mosquitoes (dengue, Zika, chikungunya) are the primary concern.

Layered Protection — More Than Skin Repellent

For any trip into a malaria zone, dense jungle, or extended outdoor exposure, the right strategy is not "more DEET." It is layered protection: skin repellent for exposed skin, permethrin-treated clothing for everywhere fabric covers, and a treated mosquito net for sleeping. Field studies of military and research personnel consistently show that the treated-uniform-plus-skin-repellent combination reduces bite rates by more than 99% — neither tool alone reaches that.

Permethrin is not a repellent in the conventional sense. It is a contact insecticide that binds to fabric and incapacitates any mosquito that lands on treated cloth. One pre-trip treatment lasts six washes (for spray-on products) up to seventy washes (for factory-treated garments). See our [permethrin clothing guide](/guides/permethrin-clothing) for the full process, including the one safety caution: keep wet-treated clothing away from cats.

At the high end of risk — single-night sleep in a rural malaria-zone guesthouse — add a permethrin-treated mosquito net. See our [mosquito nets guide](/guides/mosquito-nets-guide) for net types, mesh density (WHO minimum is 156 holes/sq inch), and setup tips. The combination of skin repellent, treated clothing, and treated net is what people on the ground in endemic areas actually use; it should be what travellers use too.

Special Cases — Pregnancy, Kids, Sensitive Skin, Pets

Pregnancy: DEET is the most studied repellent in pregnancy and is recommended by ACOG, the CDC, and WHO for pregnant women travelling to malaria-endemic destinations [1][6][7]. Picaridin has a strong safety record but less long-term data; either is reasonable in consultation with your provider, especially when the disease risk warrants protection.

Children: DEET and Picaridin are both approved for infants over two months [6][8]. OLE is not approved below three years [4][6]. IR3535 manufacturers typically list six months as a lower bound [5]. For under-two-months babies, the only protection is physical: tight-mesh stroller and crib covers, long sleeves and trousers in light fabrics, and avoiding peak-biting hours (dawn and dusk for Anopheles; mid-morning and late afternoon for Aedes).

Sensitive skin: Picaridin is the gentlest of the four for most people. OLE has a higher rate of skin reactions because of its terpenoid content; do a patch test before relying on it for a trip.

Pets: Permethrin is acutely toxic to cats — never apply wet permethrin-treated clothing near a cat, and store treated garments away from feline contact until fully dry. Picaridin and DEET are not formulated for pet use; for dogs, use a vet-approved insect repellent designed for animals.

Travel Insurance and Telehealth — The Other Half of Risk Management

No repellent strategy is 100% effective. For trips to malaria zones, dengue-active regions, or anywhere medical infrastructure is limited, two non-product layers matter as much as your spray choice: travel-medical insurance with evacuation cover, and a plan for what to do if you develop fever within 30 days of return.

Any fever 7–30 days after return from a malaria zone should be treated as potential malaria until proven otherwise — this is the single most important thing for a returning traveller to know. Tell the doctor where you have been and when you were bitten.

Frequently Asked Questions

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