Yes. Onions contain a toxic principle known as N-propyl disulfide. This compound causes a breakdown of red blood cells, leading to anemia in dogs.

The toxin causes oxidative damage to your dog’s red blood cells with attaching to the oxygen molecules in those cells. This reduces the ability of the red blood cells to carry oxygen and also tricks your dog’s body into thinking that the blood cell is an invader. The red blood cell is destroyed in a process known as hemolysis, resulting in hemolytic anemia.