All forms — raw, cooked, powdered — destroy red blood cells and cause hemolytic anemia. Onion powder hides in leftovers, soups and baby food.
Cats are even more sensitive than dogs. A single spoonful of cooked onion can poison a cat.
N-propyl disulfide oxidizes red blood cells → Heinz body anemia. Damage is dose-cumulative.
Weakness, pale gums, red-tinged urine, rapid breathing — can appear days later.
Call the vet immediately if a meaningful amount was eaten, especially for cats and small dogs.
ASPCA Animal Poison Control: (888) 426-4435 · Pet Poison Helpline: (855) 764-7661 — 24/7, a fee may apply. Your own vet first when reachable.