Causes
Common household toxins: chocolate, grapes/raisins, onion and garlic, xylitol (a sweetener), antifreeze, rodenticides, certain plants (lilies in cats · fatal), human medicines (paracetamol, ibuprofen), cleaning products, insecticides.
Diagnosis
The vet needs to know WHAT was ingested, HOW MUCH and HOW LONG AGO. Bring the product's packaging if you have it.
Treatment
DO NOT induce vomiting on your own: with some toxins (caustics, petroleum derivatives) this is dangerous. Call the vet immediately and follow their instructions. Treatment depends on the toxin (activated charcoal, antidotes, supportive care).
Prevention
Store out of reach: medicines, cleaning products, antifreeze, rodenticides. Know which plants are toxic (lilies with cats · fatal). Do not give dangerous human food.

