At a glance
| Chemical family | Phenylpyrazole — GABA receptor antagonist insecticide |
| CAS number | 120068-37-3 |
| Classification | Not IARC classified. EPA Group C (possible human carcinogen — based on thyroid tumours in rats). WHO Class II (moderately hazardous). EU banned for outdoor agricultural use (2013, bee toxicity) |
| Where you encounter it | Professional bed bug and flea treatment (sprays applied to bed frames, baseboards); pet flea products (Frontline); termite control; agricultural use (restricted in EU). Transfers from pet fur to bedding |
| Sleep micro-environment relevance | Applied to bed frames and baseboards for bed bug control. Also transfers to pillows and bedding from pets treated with fipronil-based flea products. Two pathways into the sleep environment |
Regulatory & certification status
| European Union | Banned for outdoor agricultural use since 2013 (Commission Implementing Regulation 781/2013) due to bee toxicity. Still authorised for some biocidal uses (indoor pest control). The 2017 egg scandal led to enhanced enforcement. Regulatory |
| United States | EPA-registered for residential and agricultural use. Group C (possible human carcinogen). Conditional registration for some uses. Available in pet flea products. Regulatory |
| Canada | PMRA special review of fipronil completed. Registered for pest control and pet flea products. Regulatory |
| International | WHO Class II (moderately hazardous). Not IARC classified. EU agricultural ban for bee protection. Available globally in pet flea products. Regulatory |
What it is
Fipronil is a broad-spectrum insecticide that acts by blocking GABA-gated chloride channels and glutamate-gated chloride channels (GluCls) in insect neurons, causing hyperexcitation and death. It has selectivity for insect GABA receptors over mammalian GABA receptors, providing a safety margin for human exposure. IARC has not evaluated fipronil. The US EPA classified it as Group C (possible human carcinogen) based on evidence of thyroid follicular cell tumours in rats at high doses — a mechanism that may involve disruption of thyroid hormone metabolism rather than direct genotoxicity. Fipronil gained widespread public attention in 2017 when contaminated eggs were discovered across Europe — poultry facilities had been illegally treated with fipronil, which transferred to eggs.
Where it shows up in bedding
Fipronil enters the bedroom through two pathways. First, pest control operators spray fipronil-based products on bed frames, baseboards, and room perimeters for bed bug and flea control. Second, and often overlooked, pets treated with fipronil-based flea products (Frontline, Fiproguard) transfer fipronil residues to bedding, pillows, and carpets when they sleep on or near the bed. Studies have detected fipronil and its metabolite fipronil sulfone in household dust and on surfaces where treated pets rest. For people who share beds with pets, this is a meaningful exposure pathway.
Citations
- EPA. Fipronil — Pesticide Fact Sheet. Source Regulatory
- EFSA (2013). Conclusion on the peer review of the pesticide risk assessment for bees for the active substance fipronil. Source Regulatory
- Tingle, C.C. et al. (2003). Fipronil: Environmental Fate, Ecotoxicology, and Human Health Concerns. Reviews of Environmental Contamination and Toxicology, 176: 1-66. Source Peer-reviewed
Frequently asked questions
Can my pet's flea treatment contaminate my bed?
Yes. Pets treated with fipronil-based flea products (Frontline and similar) transfer fipronil residues to surfaces they contact, including bedding, pillows, and carpets. Studies have detected fipronil and its metabolite fipronil sulfone in household dust and on surfaces where treated pets rest. If your pet sleeps on your bed, fipronil transfer to bedding is expected. The amounts are small relative to the dose applied to the pet and are not expected to cause health effects in humans.
Is fipronil a carcinogen?
IARC has not evaluated fipronil. The EPA classifies it as Group C (possible human carcinogen) based on thyroid follicular cell tumours in rats at high doses. This may involve disruption of thyroid hormone metabolism (a rat-specific mechanism) rather than direct DNA damage. The carcinogenic risk at consumer exposure levels from pest control or pet flea products is considered very low by regulatory agencies.
Related compounds
Embr is a sleep environment company researching and addressing the chemistry of the bedroom. Research and product development in progress.
Last reviewed 2026-07-08. If you find a factual error, contact us.