Onion Poisoning in Dogs.


Onion poisoning in dogs can be quite serious, so it is important to make sure your dog never eats onions, or products containing onion. In this Holidays4Dogs article, we look at why dogs shouldn’t eat onions and what to do should they accidentally do so.

We often cook onions (and garlic) and I am notoriously bad at keeping things on the work surface – (as my dogs very well know).

As a result, they tend to loiter when I am preparing dinner.

One afternoon I was busily chopping up onions to put in a vegetable soup, but I didn’t notice a small chunk fly off and land on the floor.

I only realised, because I found the wayward onion slice in the next room a short while later. Obviously, one of the dogs had swiftly and silently picked it up.

Luckily, the sneaky pooch realised it didn’t taste very nice and spat it out onto the carpet. Thankfully, dogs aren’t generally attracted to the taste of onions, but it is still important to make sure they never eat any. Onion poisoning in dogs is rare, but it can happen.

Why are onions so bad for dogs?

Onions contain a compound called N-propyl disulphide which damages red blood cells.

Onions can build up enough in the dog’s system to become toxic which can potentially lead to hemolytic anemia.  This condition can destroy a dog’s red blood cells, leaving him without enough cells for normal body function.

In severe cases, where the dog has consumed a lot of onions, or over a long period of time – the situation can be fatal.

How much onion would make my dog sick?

Thankfully, onions are not a favourite of dogs and they will usually spit them out straight away. According to experts, a dog would need to consume a considerable amount of onions to become sick.

Human foods, especially those containing onion, are bad for dogs.

While other foodstuffs, like grapes for instance, can cause problems after the dog has consumed a small amount onions at least, are a little less of a hazard in small quantities.

All the same, onions should be strictly avoided. It should also be noted that garlic, chives and leeks can also make dogs very sick.

Don’t forget either, it is not just onions themselves – there are many other foods which contain – or have been cooked with onions and are as equally bad for dogs.

Hamburgers, stuffing and many other types of food can contain onions.

As a general guide, depending on the size of dog, these quantities could be toxic:-

For small dogs around 10 lbs – 1/10th of a medium sized onion can be toxic.

Medium dogs around 30 lbs – 1/3rd of a medium sized onion could cause a toxic reaction.

Large dogs weighing around 60 lbs – 2/3rds of a medium sized onion.

If the dog already has kidney problems, consuming onion could be more serious still.

Symptoms of onion poisoning in dogs.




Tender stomach.


Breathing difficulties.

These symptoms may appear 24 hours after the dog has consumed onion, but can develop over a period of several days.

Treatment for onion poisoning in dogs.

Your vet may induce vomiting.


Medication to stop seizures.


In conclusion, it is best to keep onions completely out of reach of your pet, just in case. Remember too – there are many other products which contain onion, which your dog should not eat.

However, most dogs will recover well from the effects of consuming onions. Veterinary attention should be sought if you think your dog has eaten onions. For our article on toxic palm follow the link here.