Why is it risky?
Eucalyptus oil contains 1,8-cineole (eucalyptol) and other terpene compounds that are toxic to cats. The limited glucuronidation pathway in feline liver metabolism means these compounds are not efficiently detoxified. Both topical exposure and inhalation via diffusers can cause clinical toxicity. Eucalyptus is common in cold remedies, steam inhalation products, cleaning products, and aromatherapy blends.
Affected Systems
Nervous · Liver · Respiratory
Symptoms
Drooling, vomiting, ataxia, weakness, respiratory depression, hypothermia. Severe cases: seizures and liver damage.
What To Do
Topical exposure: wash with mild soap and water. Inhalation: move cat to fresh air. Symptomatic: emergency vet.
Notes
Eucalyptus diffuser use in a room a cat frequents is a significant risk, particularly ultrasonic diffusers that aerosolize undiluted oil. Steam inhalation bowls placed near cats for human cold remedy purposes represent high-concentration acute exposure. The eucalyptus plant itself is also toxic (same terpene compounds in leaves and bark).
Sources
→ ASPCA Animal Poison Control Center — aspca.org
→ Pet Poison Helpline — petpoisonhelpline.com
→ Merck Veterinary Manual — merckvetmanual.com