Choosing and using an insect repellent

The short answer

Pick any repellent that is registered with the U.S. Environmental Protection Agency (EPA) and lists one of four active ingredients on the label: DEET, picaridin, IR3535, or oil of lemon eucalyptus (also sold as PMD). All four are recommended by the Centers for Disease Control and Prevention (CDC), and an EPA registration number on the label means the manufacturer submitted data on the product’s safety and on how well it works against mosquitoes and ticks (1, 5).

After you choose an ingredient, match the concentration to how long you plan to be outdoors. A low-concentration product is fine for a short errand. A longer hike or evening outside calls for a higher concentration so you are not reapplying constantly. Then read and follow the label, because the label sets the reapplication timing and the age and skin cautions for that specific product (3).

The four ingredients that work

The EPA registers several active ingredients for skin-applied repellents, including DEET, picaridin, IR3535, oil of lemon eucalyptus, PMD, 2-undecanone, catnip oil, and oil of citronella (1). Of these, the CDC points people to four as reliable, well-studied choices: DEET, picaridin, IR3535, and oil of lemon eucalyptus (5).

DEET has the longest track record of the group and is the most studied. It works against both mosquitoes and ticks. Reported side effects are usually short-term eye or skin irritation (7).
Picaridin is a good alternative for people who dislike DEET’s feel or smell. Reported side effects again center on skin and eye irritation (7).
IR3535 is a synthetic repellent that has been used for years and works against mosquitoes and ticks. It can irritate the eyes and, undiluted, the skin (7).
Oil of lemon eucalyptus (OLE / PMD) is the plant-derived option among the four. It generally needs more frequent reapplication than DEET, and it is the one ingredient here with a firm age limit (see Special situations) (5, 7).

Each ingredient has its own page in this cluster:

Match concentration to time outdoors

Higher concentration does not repel insects more strongly. What it changes is how long the product keeps working before you have to reapply (7). Use this as a rough guide, and let the product label override it, because label reapplication timing is tested for that exact formula (3).

Very short trips (about an hour or two): A product with less than 10 percent active ingredient may only protect for 1 to 2 hours, which is fine for a quick errand (7).
A few hours or more outside: Choose a higher concentration so protection lasts longer between applications. For DEET specifically, the CDC recommends products with 20 percent or more (7).
Diminishing returns: More is not endlessly better. Products with more than 50 percent DEET offer no meaningful extra protection (7).

The practical takeaway: pick your ingredient first, then step up the concentration to cover the length of your outing rather than reaching for the strongest bottle on the shelf.

Special situations

Follow these population-specific cautions, which come from the CDC and the EPA:

Babies under 2 months: Do not use insect repellent. Protect infants with a mosquito net over the carrier or stroller instead (5).
Children: Do not use products with oil of lemon eucalyptus or PMD on children younger than 3 years (5, 7). For any repellent, do not let children handle the product, do not apply it to their hands, and keep it away from the eyes and mouth (3).
Pregnancy and breastfeeding: The CDC states that EPA-registered repellents, including DEET, picaridin, IR3535, oil of lemon eucalyptus, PMD, and 2-undecanone, are safe when used as directed, including for people who are pregnant or breastfeeding (5).
Sensitive skin: Reported reactions to these ingredients are usually short-term eye or skin irritation (7). Apply to a small area first, and remember that repellent goes on exposed skin or clothing, never under clothing (3).

For deeper guidance, see Repellents for children and babies and Repellents during pregnancy.

Use the EPA repellent search tool

If you want to compare specific products, the EPA hosts a free search tool called “Find the Repellent that is Right for You” (2). You tell it what you need and it returns matching products that are registered with the EPA.

You can filter by:

Which pest you need protection from (mosquitoes, ticks, or both).
How long you need protection to last.
A specific active ingredient, if you already have a preference.

The tool lists only skin-applied products that carry an EPA registration, which means the company gave the EPA technical data on the product’s safety and its effectiveness against mosquitoes and ticks (2). Two cautions from the EPA itself: one registered product can be sold under several marketing names, and not every listed product is available in every part of the country (2). The EPA does not endorse any specific product (2). The National Pesticide Information Center (NPIC) hosts a similar repellent locator (4).

What to skip

Some widely sold products are not a reliable substitute for an EPA-registered repellent:

Unregistered “natural” or botanical sprays. If a product is not registered with the EPA, the agency has not reviewed data on how well it works. Stick to the registered ingredients above. See Do natural repellents work?.
Repellent wristbands and clip-on bands. The CDC notes that repellent-impregnated wristbands are not effective at preventing bites (6). See Do repellent wristbands work?.
Ultrasonic and electronic “repeller” gadgets. The CDC lists sound-emitting devices as ineffective (6), and the Federal Trade Commission has charged sellers of electronic mosquito repellers with making false and unsubstantiated claims that they lacked evidence to support (8). See Do ultrasonic repellers work?.

Sources

EPA, “Skin-Applied Repellent Ingredients” (list of EPA-registered active ingredients for skin-applied repellents). https://www.epa.gov/insect-repellents/skin-applied-repellent-ingredients (accessed 20 July 2026).
EPA, “Find the Repellent that is Right for You” (how the repellent search tool works; what an EPA registration means; product-availability and naming cautions). https://www.epa.gov/insect-repellents/find-repellent-right-you (accessed 20 July 2026).
EPA, “Using Insect Repellents Safely and Effectively” (read the label; do not apply to children’s hands; keep away from eyes and mouth; apply only to exposed skin or clothing, not under clothing; reapply per label). https://www.epa.gov/insect-repellents/using-insect-repellents-safely-and-effectively (accessed 20 July 2026).
EPA, “Which Insect Repellent is Right for You?” (match protection time to your activity; NPIC repellent locator). https://www.epa.gov/insect-repellents/which-insect-repellent-right-you (accessed 20 July 2026).
CDC, “Preventing Mosquito Bites” (recommends DEET, picaridin, IR3535, oil of lemon eucalyptus, PMD, 2-undecanone; no repellent under 2 months; no OLE or PMD under 3 years; safe in pregnancy when used as directed). https://www.cdc.gov/mosquitoes/prevention/index.html (accessed 20 July 2026; verified via search snippet after HTTP 403 on direct fetch).
CDC Yellow Book, “Mosquitoes, Ticks, and Other Arthropods” (repellent-impregnated wristbands and sound-emitting devices are ineffective). https://www.cdc.gov/yellow-book/hcp/environmental-hazards-risks/mosquitoes-ticks-and-other-arthropods.html (accessed 20 July 2026; verified via search snippet after HTTP 403 on direct fetch).
NPIC, “Insect Repellents Fact Sheet” (concentration and duration: under 10 percent may protect 1 to 2 hours; higher concentration lasts longer but does not repel more strongly; CDC recommends DEET 20 percent or more; over 50 percent DEET adds no extra protection; OLE only for children older than 3; reported irritation effects; follow the label). https://npic.orst.edu/factsheets/repellents.html (accessed 20 July 2026).
FTC, “FTC Alleges Electronic Mosquito Repellent Claims Are False; Sellers Also Lack Evidence for Ultrasonic Pest-Control and Air Cleaning Product Claims” (2002 press release; sellers charged with false and unsubstantiated electronic mosquito repeller claims). https://www.ftc.gov/news-events/news/press-releases/2002/08/ftc-alleges-electronic-mosquito-repellent-claims-are-false-sellers-also-lack-evidence-ultrasonic (accessed 20 July 2026; verified via search snippet after HTTP 403 on direct fetch).

Ingredient comparison at a glance

Active ingredient	What it is	Works against	Duration note	Key caution
DEET	Longest-studied synthetic repellent (1, 7)	Mosquitoes and ticks (7)	CDC recommends 20 percent or more; over 50 percent adds nothing (7)	Short-term eye or skin irritation reported (7)
Picaridin	Synthetic alternative to DEET (1)	Mosquitoes and ticks (7)	Higher concentration lasts longer (7)	Skin and eye irritation reported (7)
IR3535	Long-used synthetic repellent (1)	Mosquitoes and ticks (7)	Higher concentration lasts longer (7)	Eye irritant; can irritate skin undiluted (7)
Oil of lemon eucalyptus (OLE / PMD)	Plant-derived repellent (1)	Mosquitoes (5)	Generally needs more frequent reapplication (7)	Not for children under 3; can cause eye damage (5, 7)

Educational note: This guide is general reference information, not medical advice. Always read and follow the product label, and talk to a healthcare professional about your specific situation. Last reviewed 20 July 2026.