Why is it risky?
Peppermint oil contains menthol and menthone, phenolic terpene compounds that cats cannot efficiently detoxify. Concentrated peppermint essential oil causes liver damage and neurological effects. It is common in aromatherapy blends, "natural" cleaning products, and rodent repellent sprays. It is sometimes used directly on surfaces in households with cats under the mistaken belief that cats avoid it and therefore won't be exposed.
Affected Systems
Nervous · Liver · Respiratory
Symptoms
Oral exposure: drooling, vomiting, weakness, ataxia. Inhalation: respiratory irritation, lethargy. Liver damage with significant or repeated exposure.
What To Do
Remove from exposure. Wash off if topical contact occurred. Vet if symptomatic.
Notes
Peppermint oil is marketed as a rodent repellent, some owners spray it on surfaces, thinking cats' aversion means they won't be exposed. Aversion is not protection: cats that later contact sprayed surfaces absorb the compounds through paw pads and grooming. See also: Fresh mint plant (lower risk, listed under Herbs & Aromatics). Pennyroyal (Mentha pulegium) is a mint-family member with HIGH risk from pulegone, a hepatotoxin.
Sources
→ ASPCA Animal Poison Control Center — aspca.org
→ Pet Poison Helpline — petpoisonhelpline.com