Is Eucalyptus oil safe for dogs and cats?

Eucalyptus oil (EO; primary active constituent eucalyptol/1,8-cineole, CAS 470-82-6, typically 60–90% of EO) is a GI irritant and CNS depressant in dogs at toxic doses. Exposure routes in dogs: (1) ingestion of EO-containing cleaning products, wood polishes, or topical health products; (2) dermal application of concentrated EO (some owners apply EO as a flea repellent); (3) inhalation from essential oil diffusers used extensively in the home (low-level exposure, less acute risk). Clinical signs at toxic doses: salivation, vomiting, CNS depression, ataxia, weakness. The primary concern is ingestion of concentrated products; diluted EO in commercial cleaning products at labeled concentrations is unlikely to cause severe toxicosis in dogs at incidental contact doses. Treatment: dermal decontamination if topically applied, symptomatic and supportive care. ASPCA APCC notes eucalyptus as one of the more common essential oil exposures in dogs, typically with mild to moderate outcome.

Cats are considerably more sensitive to eucalyptus oil toxicosis than dogs due to their glucuronidation deficiency (UGT enzyme), which impairs metabolism of eucalyptol and other EO terpene components. Exposure routes: (1) essential oil diffusers — ultrasonic and evaporative diffusers in enclosed spaces with cats create continuous inhalation exposure; EO particles settle on fur and are ingested during grooming, combining inhalation and ingestion routes; (2) topical application by owners attempting to repel fleas or treat skin conditions; (3) access to concentrated EO bottles or EO-containing cleaning products. Clinical signs in cats: salivation, vomiting, lethargy, ataxia, respiratory distress, tremors, hypothermia, hepatotoxicity (with repeated exposure from diffusers). Even relatively low concentrated exposure is clinically significant in cats given their metabolic limitations. Passive diffuser exposure has been associated with respiratory irritation and, with prolonged use, hepatic enzyme elevation in cats sharing enclosed spaces. Owners using EO diffusers extensively should ensure cats have access to well-ventilated areas and the diffuser is not used in enclosed spaces for prolonged periods. Any acute exposure requires immediate veterinary assessment.