# IR3535 > IR3535 is an EPA-registered insect repellent that EWG recommends at 20% concentration and that the CDC allows on children without age restriction. NPIC notes it is an eye irritant, and REI puts its typical protection at 2 to 3 hours, shorter than DEET or picaridin. **Type:** ingredients **Categories:** bug-spray **Risk Level:** caution **Evidence Strength:** moderate **Last Reviewed:** 2026-06-15 **Source:** https://www.r3recs.com/learn/ingredients/ir3535 ## Also Known As - Ethyl butylacetylaminopropionate - 3-(N-Butyl-N-acetyl)-aminopropionic acid ethyl ester - Merck 3535 ## Where Found - Skin-applied mosquito and tick repellent sprays and lotions (often around 20%) - Family and all-family formulated repellents (for example, IR3535-based all-family sprays tested by Consumer Reports) - Repellents marketed as gentle or low-odor alternatives to DEET ## Health Concerns **Eye irritation:** The most specific concern with IR3535 is eye contact. NPIC lists IR3535 as an eye irritant, so it should be kept away from the eyes and applied carefully, especially on children who may rub their faces. **Shorter protection:** IR3535 generally protects for less time than DEET or picaridin. REI puts its typical protection at 2 to 3 hours, which means more frequent reapplication and more total skin contact over a day outdoors. **Carcinogenicity:** NPIC notes that none of the common repellent ingredients, IR3535 included, have been shown to damage genes in lab tests. **General precautions:** As with all repellents, the EPA advises applying only to exposed skin, never under clothing or over cuts, wounds, or irritated skin. ## Regulatory Status **US EPA:** IR3535 is EPA-registered, meaning the manufacturer supplied technical effectiveness data; the CDC recommends EPA-registered products. **CDC:** States IR3535 can be used on children without age restriction, and that EPA-registered products are considered safe when used as directed, even for pregnant and breastfeeding women. **EWG:** Names IR3535 one of three key recommended active ingredients, at 20% concentration. **NPIC:** Documents IR3535 as an eye irritant in its repellent toxicity overview. ## Label Guide **Look for:** - An EPA registration number (EPA Reg. No.), which the CDC recommends as proof of tested effectiveness - 20% IR3535, the concentration EWG recommends - Single active ingredient (avoid combination sunscreen-plus-repellent products) **Avoid / misleading:** - Application near the eyes, since NPIC flags IR3535 as an eye irritant - Combination sunscreen-plus-repellent products (CDC advises against them) - No EPA registration number on the label ## Who Is At Risk - Children who rub their faces, since NPIC flags IR3535 as an eye irritant - Anyone applying near the eyes or face, where eye-irritation risk is highest - People spending long periods outdoors, since the shorter 2-to-3-hour protection (per REI) means more frequent reapplication ## What Helps If you choose IR3535, EWG recommends the 20% concentration, and the CDC allows it on children of any age. Because NPIC flags it as an eye irritant, keep it well away from the eyes and apply it to your own hands first before putting it on a child's face. Plan to reapply more often than with DEET or picaridin, since REI lists IR3535 protection at only 2 to 3 hours. Apply to exposed skin only, never under clothing or over broken skin, and wash it off when back indoors. For longer outings or tick-heavy areas, a 20% picaridin or DEET product will last longer. ## R3 Bottom Line - IR3535 is an EPA-registered repellent that EWG names one of three key recommended active ingredients, specifically at 20% concentration. - The CDC states IR3535 can be used on children without age restriction, alongside DEET, picaridin, and 2-undecanone, giving it a wide age window. - NPIC flags IR3535 as an eye irritant, so it should be kept well away from the eyes and applied carefully on children. - Protection tends to be shorter than DEET or picaridin: REI lists IR3535 at roughly 2 to 3 hours, so plan to reapply more often. - Apply to exposed skin only, never under clothing or over broken skin, and keep away from the eyes and mouth per the EPA. ## FAQ ### Is IR3535 safe for kids and babies? IR3535 is allowed on children of any age, with one notable caution. The CDC states IR3535 can be used on children without age restriction, alongside DEET, picaridin, and 2-undecanone. The main caveat is that NPIC flags IR3535 as an eye irritant, so keep it away from the eyes and apply it to your own hands first before putting it on a child's face. EPA-registered repellents like IR3535 are considered safe when used as directed. ### Does IR3535 work as well as DEET? IR3535 is effective but generally protects for less time than DEET. REI lists IR3535 protection at roughly 2 to 3 hours, compared with 2 to 12 hours for DEET, which means more frequent reapplication. EWG still recommends IR3535 at 20% as one of three key effective active ingredients. Consumer Reports notes that in its testing the most reliable protection has come from DEET at 25 to 30%, so for high-risk tick or disease areas, DEET or 20% picaridin will last longer than IR3535. ### What concentration of IR3535 is safe and effective? EWG recommends IR3535 at 20% concentration as one of three key effective repellent active ingredients. The CDC notes that, in general, products with less than 10% active ingredient may offer only limited protection of 1 to 2 hours, so a 20% IR3535 formula is the practical choice for meaningful protection. Even at 20%, plan to reapply more often than with DEET or picaridin, since REI puts IR3535 protection at about 2 to 3 hours. ### At what age can children use IR3535? The CDC states that IR3535 can be used on children without age restriction, the same as DEET, picaridin, and 2-undecanone. This gives it a wider age window than oil of lemon eucalyptus, which is limited to children 3 years and older. The key precaution is that NPIC flags IR3535 as an eye irritant, so it should be applied carefully and kept away from a child's eyes. ### Does IR3535 cause skin or eye irritation? The documented concern with IR3535 is eye irritation. NPIC lists IR3535 as an eye irritant, so it should be kept away from the eyes and applied carefully, particularly on children who may rub their faces. NPIC also notes that none of the common repellent ingredients, including IR3535, have been shown to damage genes in lab tests. As with all repellents, the EPA advises applying only to exposed skin and never over cuts, wounds, or irritated skin. ## Sources - [Using Insect Repellents Safely and Effectively](https://www.epa.gov/insect-repellents/using-insect-repellents-safely-and-effectively) — *US Environmental Protection Agency* (2024) - [CDC Yellow Book: Mosquitoes, Ticks, and Other Arthropods](https://www.cdc.gov/yellow-book/hcp/environmental-hazards-risks/mosquitoes-ticks-and-other-arthropods.html) — *US Centers for Disease Control and Prevention* (2024) - [Insect Repellents Fact Sheet](https://npic.orst.edu/factsheets/repellents.html) — *National Pesticide Information Center (OSU/EPA)* (2024) - [EWG's Guide to Bug Repellents](https://www.ewg.org/consumer-guides/bug-repellents) — *Environmental Working Group* (2024) - [Best Insect Repellents for You and Your Family](https://www.consumerreports.org/health/insect-repellent/best-insect-repellents-for-you-and-your-family-a4042114470/) — *Consumer Reports* (2024) - [How to Choose Insect Repellent](https://www.rei.com/learn/expert-advice/insect-repellents.html) — *REI Expert Advice* (2024) --- Source: https://www.r3recs.com/learn/ingredients/ir3535 Methodology: https://www.r3recs.com/methodology/how-we-score-products