Signs to look for
- Only ours gets ill from a treat the others ate too
- Pale gums
- Urine has gone red or dark
- Listless and breathing hard
Why it happens
That onion is dangerous to dogs is widely known. Less known is that the size of the risk differs by breed.
Allium plants such as onion and garlic contain sodium n-propylthiosulphate. It oxidises red blood cells, forming Heinz bodies; as the cells rupture, haemolytic anaemia follows.
The complication is that some breeds — Jindo, Shiba and Akita — genetically carry higher concentrations of reduced glutathione and potassium inside their red blood cells. Glutathione normally acts as an antioxidant, but against this particular toxin it does the opposite and accelerates oxidative damage.
The numbers make the gap plain. Twelve hours after being fed boiled onion, ordinary dogs had Heinz bodies in 1.2% of their red cells; dogs with this trait, 24.4%. Haemoglobin fell to 90.5% and 84.4% respectively, and measured reactive oxygen production was 4.1 times higher.
So the same quantity produces a different outcome. Allium plants are off-limits for every dog, but these breeds can run into trouble at smaller amounts.
It is not only raw onion. Cooking does not destroy the toxin, and broths, soups, sauces and marinated meat containing onion are the usual route to a real incident. Hidden sources — ramyeon broth, galbi marinade — are in fact the common ones.
Note also that the signs are delayed. Haemolysis progresses slowly and often only becomes apparent one to four days later. Looking fine straight afterwards is not reassurance.
Cats are more vulnerable than dogs. The structure of their haemoglobin leaves it prone to oxidation, so haemolysis occurs at smaller amounts than in dogs.
Other nutrition-related breed predispositions are documented. Dalmatians metabolise uric acid differently and form urate stones readily. Miniature Schnauzers are predisposed to hyperlipidaemia and pancreatitis, so high-fat treats warrant care. Siberian Huskies are known for dermatitis from impaired zinc absorption, and West Highland White Terriers for copper-storage liver disease. Beagles, Labradors and Dachshunds have a marked predisposition to obesity and gain weight on portions others hold steady on.
A predisposition is not a diagnosis, though. It is a statistic saying the risk leans that way, not a guarantee of the disease — and the same conditions occur in other breeds. Constitution varies between individuals, so where the breed is unknown, the safest course is to work to the most conservative standard.
Signs that mean go to the vet
Gums are pale or yellow
Urine is red or the colour of soy sauce — a sign of haemolysis
Listless and breathing hard
Any indication an allium plant was eaten — see a vet even without signs
Related ingredients
Related behaviour
General nutrition information. It does not replace a diagnosis or a prescription. If your animal has a medical condition or is on medication, talk to your veterinarian first.