Dogs are not recommended to eat cooked onions. Both raw and cooked onions contain a toxic component called n-propyl disulfide, which can cause oxidation of the dog’s red blood cells, leading to soluble anemia, affecting oxygen delivery, and may ultimately lead to Asphyxia due to lack of oxygen.

In addition, onions may also irritate the dog's gastrointestinal tract and cause gastroenteritis. Even small amounts of onions can cause serious health problems for dogs, so to protect your dog's health, we should avoid exposing them to onions.