Onions and garlic in all forms — powdered, raw, cooked, or dehydrated — can destroy a dog’s red blood cells, leading to anemia. That can happen even with the onion powder found in some baby food. An occasional small dose is probably OK. But just eating a large quantity once or eating smaller amounts regularly can cause poisoning. Symptoms of anemia include weakness, vomiting, little interest in food, dullness, and breathlessness.