d-trans-Allethrin
Cyclopropanecarboxylic acid, 2,2-dimethyl-3-(2-methyl-1-propenyl)-, (1S)-2-methyl-4-oxo-3-(2-propenyl)-2-cyclopenten-1-yl ester, (1R,3R)-
EPA Substance Registry Services (SRS) listed active ingredient for pesticide products.
Safety around dogs & cats
Cats cannot efficiently glucuronidate pyrethroids, so d-trans-allethrin is a real feline hazard even though its mammalian toxicity is otherwise low (ASPCA, Pet Poison Helpline, VCA, MSPCA-Angell); small exposures can cause drooling, tremors, and neuroexcitation. Keep cats away from mats, coils, and cartridges and never let one mouth the source. Dogs are far more tolerant (Merck Veterinary Manual). Keep pet birds out of enclosed treated spaces, and never apply to any animal.
High confidence. Ratings from ASPCA Animal Poison Control, the Pet Poison Helpline, and published veterinary toxicology. This is general information, not veterinary advice. If your pet is exposed, call your vet or the ASPCA Animal Poison Control Center at (888) 426-4435.
The evidence
d-trans-Allethrin is the volatile pyrethroid in classic Thermacell heat units. Field trials report high short-range protection, around 90 percent against mosquitoes within a small treated zone for several hours in calm conditions, with protection shrinking in wind and as you move away from the device.
- Application of mosquito repellent coils and associated self-reported health issues in Ghana2016Field Trial
Cross-sectional survey of coil users and self-reported respiratory health.
- Field evaluation of four spatial repellent devices against Arkansas rice-land mosquitoes2014Field TrialWell-supported evidence
Field comparison of four spatial repellent devices, including the OFF! Clip-On and Thermacell, using surrogate-human trap sites.
- A systematic review of mosquito coils and passive emanators: defining recommendations for spatial repellency testing methodologies2012ReviewWell-supported evidence
Systematic review of the spatial repellency of mosquito coils and passive emanators.
- Do mosquito coils prevent malaria? A systematic review of trials2004ReviewWell-supported evidence
Systematic review of whether mosquito coils reduce bites and prevent malaria.
- Field evaluation of an area repellent system (Thermacell) against Phlebotomus papatasi and Ochlerotatus caspius in Sanliurfa Province, Turkey2003Field TrialWell-supported evidence
Field trial of the allethrin Thermacell area repellent at multiple distances over six hours.
- Mosquito coil emissions and health implications2003Lab
Emissions study of six mosquito coil brands and their air-quality and health implications.
- Field efficacy of mosquito coil formulations containing d-allethrin and d-transallethrin against indoor mosquitoes especially Culex quinquefasciatus1990Field TrialWell-supported evidence
Field trial of d-allethrin and d-transallethrin mosquito coils in Malaysian homes, in a Culex-dominated setting.
Products using it
Regulatory notes
Source: EPA SRS active ingredient list export. Minimum risk (25(b)) status is applied separately when applicable.