Can Cats Eat Green Onions?
By Pettings · Sources checked Nov 2, 2026
No. Keep green onions away from cats. Green onions, also called scallions or spring onions, are young onion plants in the Allium genus. The ASPCA warns that Allium species can cause stomach irritation and red blood cell damage that can lead to anemia, and that cats are more susceptible than dogs. The Merck Veterinary Manual names cats as the most susceptible species to onion and garlic poisoning.
Why Green Onions Are a Problem for Cats
The ASPCA lists onion as toxic to cats and names n-propyl disulfide as its toxic principle. The Merck Veterinary Manual explains that sulfur compounds in Allium plants are released when the plant is chopped, cooked or chewed, and that they damage red blood cells, which then form Heinz bodies and break apart. Merck reports that less than a teaspoon of cooked onion has caused toxicosis in a cat. Both the white bulb and the green tops of a scallion are onion, so neither part is a better choice. Green onions often hide in foods cats might steal: sprinkled on baked potatoes, eggs and tacos, folded into fried rice, dumplings, potato salad and dips, and mixed into kimchi and stir fries. The tops are long and grassy, which can tempt a cat that likes to chew plants, so keep trimmings in a closed bin.
Signs to Watch For
The ASPCA lists vomiting, breakdown of red blood cells, blood in the urine, weakness, an elevated heart rate and panting. The Merck Veterinary Manual adds lethargy, loss of appetite, fast breathing, yellow gums or eyes, exercise intolerance and collapse. Merck notes that damage to red blood cells begins within 24 hours, with the cells usually breaking down three to five days after exposure. Signs often show up only after much of that damage has occurred, so a cat may seem normal for a few days.
What to Do If Your Cat Ate Green Onions
Call your veterinarian or the ASPCA Animal Poison Control Center at (888) 426-4435 right away. Do not try to make your cat vomit unless a vet tells you to. The Merck Veterinary Manual lists hydrogen peroxide as a way to induce vomiting in dogs only; for cats it lists a drug given by injection at the clinic. Bring the dish, recipe or package and estimate how much your cat ate. Your vet may want follow-up blood tests to look for anemia.
If your cat has a medical condition or eats a special diet, ask your veterinarian which treats fit before sharing any human food.
Common Questions
Are scallions toxic to cats?
Yes. Scallions are another name for green onions, which are young onion plants. The ASPCA lists onion as toxic to cats, with n-propyl disulfide as the toxic principle, and warns that onion-family plants can damage red blood cells. Call your veterinarian or the ASPCA Animal Poison Control Center at (888) 426-4435 if your cat ate any.
Are the green tops of green onions OK for cats?
No. The green tops are part of the same onion plant as the white bulb, and the ASPCA lists onion as toxic to cats. The grassy tops may even appeal to a cat that likes to chew greens. Keep trimmings in a closed trash can and grow cat grass instead if your cat enjoys chewing plants.
Can cats eat fried rice with green onions?
No. Fried rice usually includes green onions, and often garlic, soy sauce and salt. The ASPCA warns that onion-family plants can damage a cat's red blood cells and that excess salt can cause vomiting, diarrhea and increased thirst. If your cat ate a meaningful amount, call your veterinarian and describe what was in the dish.
How long after eating green onions will a cat get sick?
Usually a few days. The Merck Veterinary Manual explains that red blood cell damage from Allium plants begins within 24 hours, peaks around 72 hours, and the cells typically break down three to five days after exposure. Signs such as weakness, lethargy, fast breathing and dark urine tend to appear only after much damage has occurred, so call your vet right away.
Can a small amount of green onion hurt my cat?
It can, which is why vets advise against any. The Merck Veterinary Manual reports that less than a teaspoon of cooked onion has caused toxicosis in a cat, and cats are the most susceptible species. A garnish-sized nibble may or may not cause trouble, but only your veterinarian can judge the risk for your cat, so call them.