Why is it risky?
Avocado contains persin, a fungicidal toxin present in the leaves, skin, bark, and in lower concentrations in the flesh. Persin causes GI toxicity in cats. The large pit presents an additional obstruction hazard. The Guatemalan variety (most commonly sold commercially) has higher persin concentrations. Cats appear less sensitive to persin than birds or rabbits, but toxicity is documented.
Affected Systems
Digestive · Cardiovascular
Symptoms
Vomiting, diarrhea, abdominal discomfort. Large amounts: potential myocardial stress, documented primarily in birds but theoretically possible in cats with significant exposure.
What To Do
Monitor for GI symptoms if a small amount of flesh was ingested. Vet if large amount consumed or if the pit was ingested (obstruction risk independent of persin content).
Notes
Guacamole contains avocado plus onion and garlic, two independently toxic ingredients, making it significantly more dangerous than avocado alone. Avocado oil occasionally appears in "healthy cat supplement" online content, it is not an appropriate cat supplement.
Sources
→ ASPCA Animal Poison Control Center — aspca.org
→ Pet Poison Helpline — petpoisonhelpline.com/poison/avocado/