IR3535 or Lemon Eucalyptus Repellent: Which to Choose?

If you are choosing between a registered IR3535 repellent and a registered lemon eucalyptus one, start with a single question: how old is the youngest person who will wear it? On that one point CDC draws a clear line, and for many families it settles the whole decision before protection times even come up.

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Two names on the same CDC list

CDC's mosquito page lists the active ingredients it recommends in EPA-registered repellents: DEET, picaridin, IR3535, oil of lemon eucalyptus (OLE), PMD and 2-undecanone. IR3535 and OLE are both on it, and both have to arrive as a registered product with an EPA number on the label. OLE is the refined, PMD-enriched extract of the lemon-scented gum, made by repellent companies. Our oil is something else again, a steam-distilled leaf oil we sell for fragrance, and CDC says it does not recommend using "pure" oil of lemon eucalyptus as a repellent. Our comparison of OLE and the essential oil explains the distinction, and the rest of this page concerns the registered products.

The age question

CDC's consumer guidance says not to use products containing OLE or PMD on children under 3. The Yellow Book says IR3535 products can be used on children without an age restriction, while also mentioning that OLE-only products at 30% or less can be used under 3. EPA's page softens the same point: certain labels carry the under three restriction and certain OLE-only products at 30% or less do not. We would rather you take the simple route: read the label of the exact product, follow the stricter instruction if two sources seem to disagree, and ask a pediatrician about a baby. For infants under two months, EPA directs readers to a health care provider.

The handling rules are the same for both. Do not let children handle the product or apply it to their hands, put it on your own hands first and then on the child, keep it away from eyes and mouth, and wash the skin and clothes when you come indoors. Our post on lemon eucalyptus and kids adds context.

Why a single protection number should make you cautious

It is tempting to ask which lasts longer, and the evidence for IR3535 shows why an average would mislead. In EPA's science review of a Florida field study of two products, a lotion and a wipe, each with 20% IR3535, EPA concluded the data supported a complete protection time of 3 hours for both. The company that submitted the study had argued for 14 hours, and EPA did not accept that. Older laboratory work looked different again: in the 2002 New England Journal of Medicine comparison, the IR3535 repellent of the day protected for an average of 22.9 minutes, against 301.5 minutes for a 23.8% DEET formulation. Different products, different concentrations, different test designs.

The lesson we draw is practical. For either ingredient, the protection time worth trusting is the one on the label of the product in your hand, and the percentage matters. CDC's Yellow Book notes that products below 10% active ingredient might offer only limited protection, often one to two hours.

What the OLE side has going for it

PMD, OLE's key component, has a good deal of independent laboratory work behind it. A 2006 review concluded that CDC's endorsement of PMD was warranted, and a 2017 wind-tunnel study found the DEET and PMD sprays had the highest efficacy among eleven repellents it examined. That study did not include IR3535, so it cannot rank the two. Our reading is that both are legitimate registered choices: OLE comes with more lab work in the sources we reviewed, and IR3535 comes with the age advantage.

Small label details that matter

Pests. Check whether the label names mosquitoes only or ticks too. EPA's search tool, Find the Repellent that is Right for You, is a good place to compare registered products.
Sprays. EPA's rule for any spray is to apply it to your hands first for the face, and never to spray in enclosed areas.
Flammability and gear. If the label warns about flames or certain materials, believe it.

Deciding at the shelf

If you can, make this decision in person with the boxes in your hands. Pick up one of each, turn them over, and look at the same four things: the registration number, the active ingredient box, the pests named and the age line. Ten unhurried minutes there will teach you more than any comparison page, ours included. A pharmacist or the staff at an outdoor shop can often help you narrow it down.

Matching the product to the plan

Think about who is going and for how long. A short walk after dinner calls for something different from an all-day family picnic. Think about how the product feels, too, because you will only use a repellent you can tolerate: some people dislike the smell, some dislike the feel of a lotion, and some prefer the ease of a spray. Whichever you choose, the best repellent is the one that actually gets put on and reapplied on schedule.

Our short answer

Situation	Where we would start
A child under 3 is involved	Ask a pediatrician; IR3535 has no CDC age restriction, OLE and PMD do
Adults and older children who want a plant-derived option	A registered OLE or PMD product
Travel to areas with mosquito-borne illness	A travel-medicine clinic, then the product they suggest

For the wider field, see the ingredient comparison, and for the other big alternative, lemon eucalyptus versus DEET. When the bite question is settled, the lemony oil we do sell is waiting for the diffuser.