Can my dog Eats Onion?

NO

Onions, together with garlic, leek and chives are all members of the Allium family and they are all strictly forbidden for dogs. It is because onions contain an ingredient called thiosulphate which is extremely toxic to dogs. 

The thiosulphate damages the hemoglobin (substance found in red blood cells, responsible for carrying oxygen). Once the hemoglobin is damaged, the red cells containing it rupture and are consequently removed from circulation. When the amount of circulating red blood cells decreases to a certain level, the affected dog shows signs of anemia. If the amount of consumed onion is not enough to cause toxicity, it will definitely lead to gastrointestinal irritation – vomiting and diarrhea.

            Keep in mind that the amount of onions required to cause toxicity are very low. Therefore, if giving your dog store-bough foods, you need to be extra careful (because onion is found in a surprisingly wide range of food products – for example soups).

            All parts of the onion (flesh, leaves, juice) and all forms of onions (raw, cooked, dried, powdered) are toxic to dogs.