Why?
Onions contain N-propyl disulfide, a compound that damages red blood cells, causing hemolytic anemia. All forms are toxic — raw, cooked, dried, or powdered. Garlic is in the same family and is 5x more potent.
How much can dogs have?
NONE. No onions in any form or food containing onions (soups, gravies, seasonings).
What to watch out for
Symptoms may not appear for several days — include pale or yellow gums, weakness, reduced appetite, breathlessness, and collapse. Cumulative toxicity — small amounts over time build up to harmful levels.
🚨 If your dog ate onions: Contact your vet or the ASPCA Animal Poison Control Center at (888) 426-4435 right away. Don't wait for symptoms — many toxins act internally before signs appear.