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Skin-applied active

IR3535

ethyl butylacetylaminopropionate

IR3535 is a man-made repellent related to beta-alanine, which occurs naturally; it is not a plant oil.

Source and detail: CDC Yellow Book 2024, NPIC, U.S. EPA

IR3535 is a man-made repellent: EPA's January 2000 fact sheet describes it as structurally related to beta-alanine, which occurs naturally, and notes it had been used as a repellent in Europe for 20 years by then. CDC's Yellow Book files it with the biopesticide repellents, the ones derived from or synthetic versions of natural materials, rather than with DEET and picaridin, which EPA calls conventional. The mix-up to avoid is calling it a plant oil: NPIC's fact sheet says IR3535 is based on chemicals that occur in nature but is a man-made ingredient.

3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester is structurally related to β-alanine, which occurs naturally. The active ingredient is a liquid at room temperature. OPP Chemical Code: 113509 (CAS # 52304-36-6)

U.S. EPA, 3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester (IR3535) (113509) Fact Sheet, January 2000

IR3535 has been used as an insect repellent in Europe for 20 years with no substantial adverse effects. Toxicity tests show that the IR3535 is not harmful when ingested, inhaled, or used on skin.

U.S. EPA, 3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester (IR3535) (113509) Fact Sheet, January 2000

EPA characterizes the active ingredients DEET and picaridin as "conventional" repellents. The biopesticide repellents (OLE, PMD, IR3535, and 2-undecanone) are derived from, or are synthetic versions of, natural materials.

CDC Yellow Book 2024, Mosquitoes, Ticks, and Other Arthropods (Wayback Machine capture)

Oil of lemon eucalyptus and IR3535 are based off of chemicals that occur in nature but are man-made ingredients.

NPIC, Insect Repellents General Fact Sheet
EPA statusRegistered; 41 products in EPA's tool
Protection, per EPA's tool2 to 10 h mosquitoes, 2 to 12 h ticks
Youngest ageNo age limit (CDC)
GearLabels say keep it off plastics; one adds costume jewelry, leather, synthetic fibers and painted surfaces.
PetsOnly EPA's general rule applies: nothing on pets unless the label says so.

Product counts and hours are what EPA's repellent search tool listed on 2026-08-18; the other three lines are the agencies' words, sourced below.

Eleven questions.

One line each. Open any source for the full text and the exact quote.

What is it, and where does it come from?

NPIC calls IR3535 man-made, based on chemicals that occur in nature; CDC files it with biopesticide repellents.

Source and detail: CDC Yellow Book 2024, NPIC, U.S. EPA

EPA's January 2000 fact sheet describes IR3535, chemical name 3-[N-butyl-N-acetyl]-aminopropionic acid, ethyl ester, as structurally related to beta-alanine, which occurs naturally, and records its registration as an active ingredient in February 1999. NPIC's fact sheet calls it a man-made ingredient based on chemicals that occur in nature, and CDC's Yellow Book files it with the biopesticide repellents.

3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester is structurally related to β-alanine, which occurs naturally. The active ingredient is a liquid at room temperature. OPP Chemical Code: 113509 (CAS # 52304-36-6)

U.S. EPA, 3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester (IR3535) (113509) Fact Sheet, January 2000

IR3535 (chemical name: 3-[N-butyl-N-acetyl]-aminopropionic acid, ethyl ester)

CDC Yellow Book 2024, Mosquitoes, Ticks, and Other Arthropods (Wayback Machine capture)

3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester was registered (licensed for sale) as an active ingredient in February 1999. As of January 2000, there was one end product containing this active ingredient.

U.S. EPA, 3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester (IR3535) (113509) Fact Sheet, January 2000

Oil of lemon eucalyptus and IR3535 are based off of chemicals that occur in nature but are man-made ingredients.

NPIC, Insect Repellents General Fact Sheet

EPA characterizes the active ingredients DEET and picaridin as "conventional" repellents. The biopesticide repellents (OLE, PMD, IR3535, and 2-undecanone) are derived from, or are synthetic versions of, natural materials.

CDC Yellow Book 2024, Mosquitoes, Ticks, and Other Arthropods (Wayback Machine capture)

How does EPA treat it?

EPA registered IR3535 in February 1999 and now lists it in about 45 skin-applied products.

Source and detail: U.S. EPA

EPA registered IR3535 as an active ingredient in February 1999, and its January 2000 fact sheet says the one product then registered met the effectiveness and safety standards EPA requires of products used against public health pests. EPA's skin-applied ingredients page, updated January 2026, now lists IR3535 in about 45 registered products.

3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester was registered (licensed for sale) as an active ingredient in February 1999. As of January 2000, there was one end product containing this active ingredient.

U.S. EPA, 3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester (IR3535) (113509) Fact Sheet, January 2000

To help protect the public's health, EPA requires registrants of products used against public health pests to demonstrate that the products meet specific standards for effectiveness as well as for safety. The product currently registered with 3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester as the active ingredient has met the applicable standards.

U.S. EPA, 3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester (IR3535) (113509) Fact Sheet, January 2000

IR 3535 -- EPA pesticide regulatory information (3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester) (about 45 products)

U.S. EPA, Skin-Applied Repellent Ingredients, last updated January 23, 2026

What strengths are registered, and does strength change protection?

Labels declare 20 and 19.7 percent; CDC says higher concentrations generally protect longer.

Source and detail: CDC Yellow Book 2024, Carroll JF, U.S. EPA accepted label

Two accepted labels declare the active at 20 percent (EPA Reg. No. 54287-20) and 19.7 percent (EPA Reg. No. 806-32). In a 2010 Journal of Medical Entomology tick trial, the 10 percent IR3535 lotion was significantly less effective than formulations with higher concentrations of repellent, and CDC's Yellow Book says higher concentrations of active ingredient generally provide longer protection, regardless of the active.

ACTIVE INGREDIENT: 3-((N-butyl-N-acetyl)-amino propionic acid ethyl ester*..............................................................20% OTHER INGREDIENTS:............................................................80%

U.S. EPA accepted label, Super Guard 3535 Insect Repellent, EPA Reg. No. 54287-20, December 17, 2015

ACTIVE INGREDIENT: 3-[N-butyl-N-acetyl]-aminopropionic acid, ethyl ester* 19.7% OTHER INGREDIENTS: 80.3% TOTAL: 100.0%

U.S. EPA accepted label, Avon Skin-So-Soft SSS Bug Guard Plus IR3535 Expedition Insect Repellent SPF 30, EPA Reg. No. 806-32, January 23, 2018

The 10% IR3535 lotion was significantly less effective than the formulations with higher concentrations of repellent. In the formulations tested, deet, picaridin, and IR3535 provided lasting protection against A. americanum.

Carroll JF, Benante JP, Kramer M, Lohmeyer KH, Lawrence K. Formulations of deet, picaridin, and IR3535 applied to skin repel nymphs of the lone star tick (Acari: Ixodidae) for 12 hours. J Med Entomol. 2010 Jul;47(4):699-704. PMID 20695288

In general, higher concentrations of active ingredients provide longer duration of protection, regardless of the active ingredient.

CDC Yellow Book 2024, Mosquitoes, Ticks, and Other Arthropods (Wayback Machine capture)

How long does EPA say it protects?

One label says reapply after 12 hours for deer ticks, 8 for mosquitoes and 6 for gnats.

Source and detail: U.S. EPA, U.S. EPA accepted label

The accepted label for Avon Skin-So-Soft Bug Guard Plus IR3535 Expedition (EPA Reg. No. 806-32, 19.7 percent) says reapply after 12 hours for deer ticks, 8 hours for mosquitoes and 6 hours for gnats, no-see-ums, sand flies and biting midges. EPA's search tool, whose database EPA says was last updated in June 2019, lists Superguard 3535 (EPA Reg. No. 54287-20, 20 percent) at 8 hours for mosquitoes, with no tick registration.

FOR PROTECTION from deer ticks reapply after 12 hours, and for mosquitoes reapply after 8 hours, and for gnats, no-seeums, sand flies and biting midges reapply after 6 hours.

U.S. EPA accepted label, Avon Skin-So-Soft SSS Bug Guard Plus IR3535 Expedition Insect Repellent SPF 30, EPA Reg. No. 806-32, January 23, 2018

| Superguard 3535 Insect Repellent (SPF 20) | 8 | X | IR3535 | 20 | Associated Registrations | 54287-20

U.S. EPA, Insect Repellents: Use and Effectiveness search results for IR3535

Product Name Hourly Protection Time for Mosquitoes Hourly Protection Time for Ticks Active Ingredient(AI) AI% in Product Formula Company Name EPA Registration Number

U.S. EPA, Insect Repellents: Use and Effectiveness search results for 2-undecanone

An asterisk ( * ) indicates that EPA has technical information on the effectiveness of the product against mosquitoes and/or ticks and the company chose not to have a specific time associated with their product. * An " X " indicates that the repellent product has not been registered for protection from ticks.

U.S. EPA, Insect Repellents: Use and Effectiveness search results

Any products listed are for informational purposes only. Inclusion of a product listed/referenced is not an endorsement. * EPA and the U.S. Government do not endorse any product or service. * The information in this database was last updated in June 2019.

U.S. EPA, Find the Repellent that is Right for You

ACTIVE INGREDIENT: 3-[N-butyl-N-acetyl]-aminopropionic acid, ethyl ester* 19.7% OTHER INGREDIENTS: 80.3% TOTAL: 100.0%

U.S. EPA accepted label, Avon Skin-So-Soft SSS Bug Guard Plus IR3535 Expedition Insect Repellent SPF 30, EPA Reg. No. 806-32, January 23, 2018

Which pests do accepted labels name, and what does CDC say those pests carry?

EPA lists mosquitoes, deer ticks, body lice and biting flies; a label adds gnats, no-see-ums and sand flies.

Source and detail: CDC, U.S. EPA, U.S. EPA accepted label

EPA's 2000 fact sheet lists IR3535's target pests as mosquitoes, deer ticks, body lice and biting flies; the accepted label for EPA Reg. No. 806-32 claims repellency against deer ticks, mosquitoes, gnats, no-see-ums, sand flies and biting midges. CDC says some U.S. ticks carry pathogens that can cause Lyme disease and Powassan virus, and that mosquitoes can spread pathogens through bites, naming West Nile virus, dengue and malaria.

o Use Sites: Human skin. o Target Pests: Mosquitoes, deer ticks, body lice, and biting flies.

U.S. EPA, 3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester (IR3535) (113509) Fact Sheet, January 2000

Strong [repellency] [protection] against deer ticks, mosquitoes, gnats, no-seeums, sand flies and biting midges

U.S. EPA accepted label, Avon Skin-So-Soft SSS Bug Guard Plus IR3535 Expedition Insect Repellent SPF 30, EPA Reg. No. 806-32, January 23, 2018

In the United States, some ticks carry pathogens that can cause human disease, including: * Alpha-gal syndrome * Anaplasmosis * Babesiosis * Bourbon virus * Colorado tick fever * Ehrlichiosis * Hard tick relapsing fever * Heartland virus * Lyme disease * Powassan virus * Rickettsia parkeri rickettsiosis * Rocky Mountain spotted fever * Soft tick relapsing fever * STARI * Tularemia

CDC, About Ticks and Tickborne Disease (Wayback Machine capture of cdc.gov/ticks/about/index.html)

Almost everyone has been bitten by a mosquito. Mosquitoes can spread pathogens (germs) through bites. A person who gets bitten by a mosquito and gets sick has a mosquito-borne disease like West Nile virus, dengue, or malaria.

CDC, About Mosquitoes (Wayback Machine capture of cdc.gov/mosquitoes/about/index.html)

What do the agencies say about children?

CDC says no age restriction; one label says ask a doctor under 6 months, adult applies under 10.

Source and detail: CDC Yellow Book 2024, U.S. EPA accepted label

CDC's Yellow Book says repellents containing IR3535 can be used on children without age restriction. The accepted labels carry their own cautions: EPA Reg. No. 806-32 says ask a doctor for children under 6 months and that an adult must apply it to children under age 10, and EPA Reg. No. 54287-20 says use on children under 6 months only with the advice of a physician.

Insect repellents containing DEET, picaridin, IR3535, and 2-undecanone can be used on children without age restriction (see EPA webpage on Using Insect Repellents Safely and Effectively with Children ).

CDC Yellow Book 2024, Mosquitoes, Ticks, and Other Arthropods (Wayback Machine capture)

An adult must apply this product to children under age 10. Children under 6 months: Ask a doctor. Do not apply over wounds, freshly shaved or irritated skin.

U.S. EPA accepted label, Avon Skin-So-Soft SSS Bug Guard Plus IR3535 Expedition Insect Repellent SPF 30, EPA Reg. No. 806-32, January 23, 2018

CAUTION: For external use only. Causes moderate eye irritation. Do not get in eyes. Use on children under 6 months of age only with the advice of a physician.

U.S. EPA accepted label, Super Guard 3535 Insect Repellent, EPA Reg. No. 54287-20, December 17, 2015

What do CDC and WHO say about pregnancy?

CDC says EPA recommends no precautions for pregnant or lactating women beyond its usual repellent tips.

Source and detail: CDC Yellow Book 2024, NPIC, World Health Organization

CDC's Yellow Book says EPA recommends no precautions beyond its usual tips for using registered repellents on women who are pregnant or lactating, and NPIC reports that CDC recommends an EPA-registered repellent with DEET, picaridin, IR3535 or oil of lemon eucalyptus for pregnant mothers in areas with Zika risk. WHO's malaria and dengue fact sheets name IR3535 among the repellents they list, and neither fact sheet we read ties a repellent choice to pregnancy.

Other than the safety tips listed above, EPA does not recommend any additional precautions for using registered repellents on children or on women who are pregnant or lactating.

CDC Yellow Book 2024, Mosquitoes, Ticks, and Other Arthropods (Wayback Machine capture)

CDC also recommends the use of an EPA-registered repellent with DEET, picaridin, IR3535, or oil of lemon eucalyptus for pregnant mothers in areas with risk of Zika. 28 Consult a healthcare professional for more information.

NPIC, Insect Repellents General Fact Sheet

Use mosquito repellents (containing DEET, IR3535 or Icaridin) after dusk.

World Health Organization, Malaria fact sheet

To lower your risk of getting dengue, protect yourself from mosquito bites by using: * clothes that cover as much of your body as possible; * mosquito nets, ideally sprayed with insect repellent, if sleeping during the day; * window screens; * mosquito repellents (containing DEET, Picaridin or IR3535); and * coils and vaporizers.

World Health Organization, Dengue and severe dengue fact sheet

What do NPIC and EPA report about absorption and toxicity?

NPIC rates oral, inhalation and dermal toxicity very low, eye irritation moderate; undiluted IR3535 can irritate skin.

Source and detail: NPIC, U.S. EPA

EPA's 2000 fact sheet says toxicity tests show IR3535 is not harmful when ingested, inhaled or used on skin. NPIC's fact sheet rates it very low for oral, inhalation and dermal toxicity and moderate for eye irritation; NPIC adds that undiluted IR3535 can cause skin irritation, that skin irritation was not reported in studies with diluted IR3535, and that feeding studies show concentrated IR3535 is low in developmental and reproductive toxicity.

IR3535 has been used as an insect repellent in Europe for 20 years with no substantial adverse effects. Toxicity tests show that the IR3535 is not harmful when ingested, inhaled, or used on skin.

U.S. EPA, 3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester (IR3535) (113509) Fact Sheet, January 2000

| IR3535 13 | Very Low | Very low | Very Low | Moderate | Very low

NPIC, Insect Repellents General Fact Sheet, Table 1. Short-Term Toxicity of Active Ingredients in Common Insect Repellents

IR3535 : IR3535 is an eye irritant. Human and animal studies show if it is undiluted, it can cause skin irritation. In studies with diluted IR3535, skin irritation was not reported. 18,19

NPIC, Insect Repellents General Fact Sheet

IR3535 : Multiple feeding studies show concentrated IR3535 is low in developmental and reproductive toxicity. 19,22

NPIC, Insect Repellents General Fact Sheet

Does it damage plastics, fabrics or gear?

Labels say keep it off plastics; one adds costume jewelry, leather, synthetic fibers and painted surfaces.

Source and detail: U.S. EPA accepted label

Two accepted labels say to keep it off plastics. EPA Reg. No. 806-32 says avoid contact with plastics, costume jewelry, leather and synthetic fibers, and that it may damage painted or varnished surfaces, including nail polish; EPA Reg. No. 54287-20 says the product contains alcohol and to avoid contact with plastics.

Avoid contact with plastics, costume jewelry, leather and synthetic fibers. May damage painted or varnished surfaces, including nail polish.

U.S. EPA accepted label, Avon Skin-So-Soft SSS Bug Guard Plus IR3535 Expedition Insect Repellent SPF 30, EPA Reg. No. 806-32, January 23, 2018

PHYSICAL OR CHEMICAL HAZARDS: Flammable. Keep away from heat and open flame. Contains alcohol. Avoid contact with plastics.

U.S. EPA accepted label, Super Guard 3535 Insect Repellent, EPA Reg. No. 54287-20, December 17, 2015

What do the agencies say about pets?

Only EPA's general rule applies: nothing on pets unless the label says so.

Source and detail: U.S. EPA

No IR3535 label we read mentions pets or other animals. The rule that applies is EPA's general one: do not use any repellent product on pets or other animals unless the label clearly states it is for animals.

Do not use any product on pets or other animals unless the label clearly states it is for animals.

U.S. EPA, Using Insect Repellents Safely and Effectively

Which studies are on the record?

A 2008 controlled-release trial: 7.1 to 10.3 hours against field mosquitoes, 9.1 to 12.2 against lab ticks.

Source and detail: Carroll JF, Carroll JF. Prolonged efficacy of IR3535 repellents against mosquitoes and blacklegged ticks in North America. J Med Entomol. 2008 Jul;45(4):706-14. PMID 18714871

Carroll et al., Journal of Medical Entomology 2010: formulations of 20 percent or more, IR3535 among them, let fewer than 10 percent of lone star ticks cross treated bands over 12 hours; the 10 percent IR3535 lotion was significantly less effective. Carroll, same journal, 2008, tested controlled-release IR3535 formulations at 10 and 20 percent: complete protection times of 7.1 to 10.3 hours against mosquitoes in the field and 9.1 to 12.2 hours against blacklegged ticks in the laboratory.

Formulations containing > or = 20% active ingredient were highly effective, with <10% of the ticks crossing through the treatment bands for any challenge during the 12 h. At least 40% of ticks exposed to any formulation for any challenge fell or crawled off the volunteers. There was no difference in effectiveness between the 20% spray and 20% lotion formulations of picaridin.

Carroll JF, Benante JP, Kramer M, Lohmeyer KH, Lawrence K. Formulations of deet, picaridin, and IR3535 applied to skin repel nymphs of the lone star tick (Acari: Ixodidae) for 12 hours. J Med Entomol. 2010 Jul;47(4):699-704. PMID 20695288

The 10% IR3535 lotion was significantly less effective than the formulations with higher concentrations of repellent. In the formulations tested, deet, picaridin, and IR3535 provided lasting protection against A. americanum.

Carroll JF, Benante JP, Kramer M, Lohmeyer KH, Lawrence K. Formulations of deet, picaridin, and IR3535 applied to skin repel nymphs of the lone star tick (Acari: Ixodidae) for 12 hours. J Med Entomol. 2010 Jul;47(4):699-704. PMID 20695288

Complete protection times ranged from 7.1 to 10.3 h for mosquitoes and from 9.1 to 12.2 h for blacklegged ticks. Long protection duration resulted in many cases being truncated by darkness or eventual subject withdrawal, which suggests that actual protection times were probably greater.

Carroll JF. Prolonged efficacy of IR3535 repellents against mosquitoes and blacklegged ticks in North America. J Med Entomol. 2008 Jul;45(4):706-14. PMID 18714871

I tested novel, controlled-release formulations of IR3535, at 10% in lotion and at 20% in pump spray and aerosol, against mosquitoes in the field and blacklegged ticks in the laboratory.

Carroll JF. Prolonged efficacy of IR3535 repellents against mosquitoes and blacklegged ticks in North America. J Med Entomol. 2008 Jul;45(4):706-14. PMID 18714871

Put it beside another.

IR3535 vs DEETIR3535 vs PicaridinIR3535 vs Permethrin

All ten actives 631 products by ingredient

Sources on this page.

16 sources. Every quote was fetched on or before 2026-09-22 and is stored with the page. Last reviewed 2026-09-22.

  1. U.S. EPA, 3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester (IR3535) (113509) Fact Sheet, January 2000. https://www3.epa.gov/pesticides/chem_search/reg_actions/registration/fs_PC-113509_01-Jan-00.pdf
  2. CDC Yellow Book 2024, Mosquitoes, Ticks, and Other Arthropods (Wayback Machine capture). https://wwwnc.cdc.gov/travel/yellowbook/2024/environmental-hazards-risks/mosquitoes-ticks-and-other-arthropods
  3. NPIC, Insect Repellents General Fact Sheet. https://npic.orst.edu/factsheets/repellents.html
  4. U.S. EPA, Skin-Applied Repellent Ingredients, last updated January 23, 2026. https://www.epa.gov/insect-repellents/skin-applied-repellent-ingredients
  5. U.S. EPA accepted label, Super Guard 3535 Insect Repellent, EPA Reg. No. 54287-20, December 17, 2015. https://www3.epa.gov/pesticides/chem_search/ppls/054287-00020-20151217.pdf
  6. U.S. EPA accepted label, Avon Skin-So-Soft SSS Bug Guard Plus IR3535 Expedition Insect Repellent SPF 30, EPA Reg. No. 806-32, January 23, 2018. https://www3.epa.gov/pesticides/chem_search/ppls/000806-00032-20180123.pdf
  7. Carroll JF, Benante JP, Kramer M, Lohmeyer KH, Lawrence K. Formulations of deet, picaridin, and IR3535 applied to skin repel nymphs of the lone star tick (Acari: Ixodidae) for 12 hours. J Med Entomol. 2010 Jul;47(4):699-704. PMID 20695288. https://pubmed.ncbi.nlm.nih.gov/20695288/
  8. U.S. EPA, Insect Repellents: Use and Effectiveness search results for IR3535. https://cfpub.epa.gov/oppref/insect_s/search_results.cfm?Rangetime=&hidSelected=1&ProductName=&Ingredient=IR3535&Company=null&Registration=
  9. U.S. EPA, Insect Repellents: Use and Effectiveness search results for 2-undecanone. https://cfpub.epa.gov/oppref/insect_s/search_results.cfm?Rangetime=&hidSelected=1&ProductName=&Ingredient=2-undecanone&Company=null&Registration=
  10. U.S. EPA, Find the Repellent that is Right for You. https://www.epa.gov/insect-repellents/find-repellent-right-you
  11. CDC, About Ticks and Tickborne Disease (Wayback Machine capture of cdc.gov/ticks/about/index.html). https://www.cdc.gov/ticks/about/index.html
  12. CDC, About Mosquitoes (Wayback Machine capture of cdc.gov/mosquitoes/about/index.html). https://www.cdc.gov/mosquitoes/about/index.html
  13. World Health Organization, Malaria fact sheet. https://www.who.int/news-room/fact-sheets/detail/malaria
  14. World Health Organization, Dengue and severe dengue fact sheet. https://www.who.int/news-room/fact-sheets/detail/dengue-and-severe-dengue
  15. U.S. EPA, Using Insect Repellents Safely and Effectively. https://www.epa.gov/insect-repellents/using-insect-repellents-safely-and-effectively
  16. Carroll JF. Prolonged efficacy of IR3535 repellents against mosquitoes and blacklegged ticks in North America. J Med Entomol. 2008 Jul;45(4):706-14. PMID 18714871. https://pubmed.ncbi.nlm.nih.gov/18714871/