Can Dogs Eat Onions and Peppers?

Photo by Jenna Ebert on Unsplash

In today’s article, I’m going to write about another popular veg combo that people want to feed to their dogs.

You might have read my article about feeding dogs broccoli and cauliflower– which by the way is a great combination.  

The combination in today’s article isn’t as straightforward as that one because one of the vegetables in the combo is highly toxic to dogs- onions. 

Which is a shame because onions and peppers are used in many popular recipes such as chilli con carne or fajitas.

And it makes life so much easier if we can prepare something for our dogs at the same time as preparing something for ourselves.

But if feeding our dogs onions and peppers isn’t to be, let me tell you why it is so unsuitable..

Can dogs eat onions and peppers?

Onions are extremely toxic to dogs and the only way to guarantee that they won’t be poisoned by eating any is to make sure that they never eat any.

Although onions aren’t so toxic that they will kill a dog as soon as he sniffs one the amount of onion that a dog can safely eat is so small that it just isn’t worth the risk. 

And this applies to all forms of onions- yellow green or red coloured ones, diced onions, chopped onions, onion powder.

I wouldn’t even let my dog get near an onion dip or a packet of onion crisps just to be on the safe side.

And it isn’t just onions- the whole family is rotten and toxic.

Garlic, leeks, shallots, chives..

So, what makes onions so bad?

Why are onions toxic?

Onions are toxic to dogs because they contain a substance called n-propyl disulphide.

Dogs cannot process this disulphide and so it acts like a poison within their bodies.

It attaches itself to the outside of red blood cells and destroys them.

Without enough red blood cells to carry oxygen around their bodies dogs become anaemic and if they aren’t treated could die. 

How much onion can kill a dog?

Like all toxins, there is a relationship between the amount of toxin ingested and the size of a dog.

The larger the dog the more onion they can consume before being poisoned.

There are two methods that can be used to calculate onion toxicity.

The first is that a dog can consume up to 15 g of onion for every kg that they weigh. 

Or you can say that they can eat the equivalent of .5% of their body weight in onions before they will put themselves at any risk.

Let me give you a few examples to highlight how different sized dogs are at risk. 

Firstly, a Yorkshire Terrier. These are a very popular dog (the 12th most popular on the AKC breed list 2019.)

Weighing around 7 pounds or just over 3 kilograms, Yorkies can eat about 15 g of onion before they are placing themselves in any danger.

15 g equals .5% of their bodyweight. 

Now 15 g is nothing.

You can see a photo that I have taken of a very small onion that I have at home. 

It is next to a tiny plum tomato and a peg to try and give you an idea of how small it is.

I weighed the onion and even though it is small it weighs 39 g.

That is well over double the amount of onion needed to potential kill a Yorkshire Terrier.

The next example is one of my Golden Retrievers, Sylvie- who weighs around 66 pounds or 30 kg.

Again using the .5% bodyweight ratio, Sylvie can eat 150 g of onion which is about four of those small onions in the photo. 

There is a huge difference in the amount of onions that these two sizes of dog can eat because there’s a huge difference in their body weight.

But in the big scheme of things the amount of onion that either breed of dog can consume safely is tiny- particularly if the onion is mixed in with other ingredients such as meat. 

How long after eating onions will a dog get sick?

It might be a few days after eating an onion that a dog shows any sign of onion poisoning- for the red blood cells to have begun to have been destroyed in any real numbers.

Another important point is that a dog can be poisoned by onions in one go- eating more than .5% of their body weight in one raid of the kitchen counter or over several days.

For instance you might be feeding your dog some leftover casserole over a few days and if the onion content is high enough then this could also put them in danger.

It all sounds a bit grim, doesn’t it?

What are the symptoms of onion poisoning?

So what are the telltale signs that your dog is in danger?

Well, there are two sets of signs. 

The first are related to the dog being physically sick- vomiting, diarrhea or lethargy could all be in evidence.

And then as the blood cells begin to die off you could see signs of anaemia- rapid heart rate and breathing, pale gums (in the mouth) and extreme lethargy. 

If you see any of these symptoms after an incident where you know that your dog has eaten onions, you must take them to the vets as soon as possible.

The best way to protect your dog against the dangers of onion poisoning is to never let them eat one.

This is a much easier rule to follow than trying to calculate the exact amount of onion that you can add into their diet safely. 

Hopefully we have finished with the bad news.

As we think about peppers, things are looking up. 

What nutrition do peppers have?

Bell peppers aren’t toxic to your dog and don’t threaten their health in any way.

In fact with the nutrients and vitamins that they contain they are a great snack to feed to your dog raw or cooked they can be added to their main meal.

Peppers are obviously low in calories but they are quite high in fibre (just below 2%.)

Vitamin wise, they are particularly high in vitamin C and B6-.

Vitamin B6 is important when it comes to keeping the cells within a dog’s body healthy.

And there is a certain irony in this when we have talked at length about how onion toxicity kills those cells!

They provide some vitamin E and vitamin K in smaller concentrations. 

Mineral- wise copper and potassium seem to be the big hitters. 

Copper helps to maintain a healthy heart, bones and muscles. 

Potassium helps to maintain a healthy heart beat as well as making sure that a dog’s nerves are in optimum condition.  

Can dogs eat green peppers?

How unpopular are green peppers? 

Is one way to get rid of them to feed them to your dog?

Dogs can eat any colour of pepper- red, yellow, orange or green.

The most obvious differences between these different colours of pepper is that they taste different- green is more bitter whereas red and orange peppers are sweeter.

Interestingly, there are some differences when it comes to the nutrients they contain.

Green peppers have the fewest calories, whereas red peppers have the highest amount of fibre.

Red peppers contain more significantly Riboflavin (B2) than yellow or green peppers.

But when it comes to vitamin C, yellow peppers are streets ahead!

All three colours contain quite a bit of vitamin B6 but once again red peppers top the poll. 

In terms of mineral, copper is the main one in all three colours but yellow peppers do contain significantly more. 

So if you are looking for an excuse to feed green peppers to your dog then they are the lowest in calories. 

What other vegetable could I combine with peppers?

As long as you stay away from onions, garlic and tomatoes then the choice of other vegetables that you can have with peppers is incredibly varied.

Oh and dogs really shouldn’t touch asparagus

You might want to try a dark green vegetable like broccoli or even cauliflower leaves.

These bring a different mix of vitamins and minerals.

More vitamin A, which is great for a dog’s eyesight as well as larger doses of Phosphorus and Manganese.

And of course the texture is different.

If you are using peppers as a snack and you want to add something which is different, try frozen carrots.

Now that is a completely different experience- perfect for the long hot days of summer. 

James Grayston

My name is James and I love dogs. have owned four Golden Retrievers in the past 15 years. Currently I own two "Goldies"- a five year old and a seven month old. The photo shows me with our youngest when she was about 7 weeks old!