I knew that dogs mustn't be given chocolate as it is toxic to them but I didn't know about onions. I came across this while researching Bonnie's recent illness. It is important that we're very careful about feeding our pets. Just because they will eat something doesn't mean they should have it.
As far as I know Bonnie didn't eat onions before she became ill but before reading this I wouldn't have considered it harmful to give her, or any of the dogs, leftover stew or other onion-laced meaty dish. I know better now.
Onions and garlic are other dangerous food ingredients that cause sickness in dogs, cats and also livestock. Onions and garlic contain the toxic ingredient thiosulphate. Onions are more of a danger.
Pets affected by onion toxicity will develop haemolytic anaemia, where the pet’s red blood cells burst while circulating in its body. (This is what Bonnie was treated for)
At first, pets affected by onion poisoning show gastroenteritis with vomiting and diarrhoea. They will show no interest in food and will be dull and weak. The red pigment from the burst blood cells appears in an affected animal’s urine and it becomes breathless. The breathlessness occurs because the red blood cells that carry oxygen through the body are reduced in number.
The poisoning occurs a few days after the pet has eaten the onion. All forms of onion can be a problem including dehydrated onions, raw onions, cooked onions and table scraps containing cooked onions and/or garlic. Left over pizza, Chinese dishes and commercial baby food containing onion, sometimes fed as a supplement to young pets, can cause illness.
Onion poisoning can occur with a single ingestion of large quantities or with repeated meals containing small amounts of onion. A single meal of 600 to 800 grams of raw onion can be dangerous whereas a ten-kilogram dog, fed 150 grams of onion for several days, is also likely to develop anaemia. The condition improves once the dog is prevented from eating any further onion
While garlic also contains the toxic ingredient thiosulphate, it seems that garlic is less toxic and large amounts would need to be eaten to cause illness.