Dogs will generally have a poisoning reaction within 1 to 3 days after eating onions. If there is no poisoning reaction within 3 days, it means the dog is fine. If a dog shows obvious signs of poisoning after eating onions, the owner is best to take it to the pet hospital for infusion and detoxification as soon as possible to avoid threatening the dog's life.
If a dog is seriously poisoned after eating onions, he will have blood in the urine, foaming at the mouth, convulsions, and breathing. Symptoms of difficulty, vomiting, and even death. If the poisoning is mild, symptoms usually include depression, poor appetite, and light red urine.