Insect repellent does not usually kill bugs — it hides you from them, blocking the scent cues mosquitoes and ticks use to find a meal.
Spray on an EPA-registered repellent and that trail goes quiet: depending on the active ingredient, the bug either loses your scent or loses interest in landing, so the bite never happens.
Does Insect Repellent Kill Insects Or Just Repel Them?
Repellents applied to skin stop bites — they are not designed to kill. The EPA describes DEET, the most-studied active ingredient, as working by blocking an insect’s ability to smell humans. Other registered ingredients interfere with the bug’s ability to find a host or deter it from landing and biting. Either way, the insect flies off unharmed and unfed.
A repellent that quiets your scent protects everyone nearby far less than it protects you — the bug simply looks for a different target. If you want bugs to die, that is an insecticide’s job.
Which Ingredients Actually Work, And How Long Do They Last?
The EPA’s list includes DEET, picaridin, IR3535, p-Menthane-3,8-diol (PMD), oil of lemon eucalyptus (OLE), 2-undecanone, catnip oil, and citronella oil.
Picaridin is called KBR 3023 and goes by icaridin outside the United States — same chemical, different label. OLE and PMD are related but not identical: PMD is the refined, registered version.
Higher percentages mean longer protection, not stronger protection. A 10% and a 30% DEET product both work; the stronger one buys more hours before reapplication. Reapplication timing comes from the label, and the label always wins.
| Active Ingredient | EPA-Registered Products | Notes |
|---|---|---|
| DEET | More than 500 | Blocks insects’ ability to smell humans; acts immediately |
| Picaridin (icaridin) | About 40 | Conventional repellent; called KBR 3023 |
| IR3535 | About 45 | Long-lasting registered active |
| OLE | 6 | Not for children under 3 |
| PMD | 6 | Refined form of OLE; not for children under 3 |
| 2-undecanone | 1 | Long-lasting registered active |
Product counts come from the EPA’s skin-applied repellent ingredients page. To compare ready-made options, our tested roundup of the best insect repellent options puts real-world picks side by side.
How Should You Apply It So It Actually Works?
Follow the label exactly — the label sets the dose and reapplication timing, and more product is not better. EPA guidance:
- Apply only to exposed skin or clothing, never underneath clothing.
- Keep it away from eyes and mouth, and apply sparingly around the ears.
- With sprays, put it on your hands first, then wipe it onto your face — never spray directly at your face.
- Skip cuts, wounds, and irritated skin.
- Do not spray in enclosed areas.
- With sunscreen too, apply sunscreen first, then repellent.
- Wash treated skin once indoors, and wash treated clothing separately.
DEET-containing repellents act immediately on application, making them a good pick right before entering a biting zone. OLE and PMD should not be used on children under 3 because of potential allergic skin reactions — a DEET or picaridin product is better there.
Why Do Some Repellents Seem To Fail?
Almost every “it didn’t work” story traces back to application, not the ingredient. Spraying under clothing wastes product and leaves exposed skin unprotected. Overapplying does not extend protection and can irritate skin. Using unregistered “pure” OLE means relying on a product never validated for repellency. And skipping the reapply window on a hot, sweaty day cuts protection short.
The fix: pick an EPA-registered product with a long-lasting active, follow its label for amount and timing, and reapply on schedule.
Common Questions
Does DEET kill mosquitoes?
No. DEET blocks a biting insect’s ability to smell humans, so the mosquito fails to find you rather than dying. The EPA describes this scent-blocking mechanism specifically. A DEET product reduces bites without killing the insect, which is why it is classified as a repellent and not an insecticide.
Can kids use oil of lemon eucalyptus?
Not under age 3. OLE and its refined form, PMD, should be skipped for children younger than 3 because of potential allergic skin reactions. For younger children, choose a different EPA-registered active ingredient and follow that product’s label directions for amount and reapplication timing.
Should you put repellent under your clothes?
No. Apply repellent only to exposed skin or clothing, never underneath your clothing. Covering treated skin traps the product against your body, wastes it, and does nothing for the skin you left exposed.
Sources
- U.S. Environmental Protection Agency. “Skin-Applied Repellent Ingredients.” Lists all registered actives and product counts by ingredient.
- U.S. Environmental Protection Agency. “Using Insect Repellents Safely and Effectively.” Source of the application and reapplication guidance.
- U.S. Environmental Protection Agency. “DEET.” Explains DEET’s scent-blocking mechanism and immediate action.