Can Dogs Eat Onion?

babel · December 27, 2022
This content was reviewed and approved by the biologist Samuel Sanchez on July 25, 2021
Onions contain thiosulfate. Find out the effects of this sulfuric compound on dogs.

People often decide to include their own food in their dogs’ diet. However, it’s important to clarify that not everything that’s part of the human diet is equally good for canines, as their metabolism is different. Hence the question: can dogs eat onion?

It’s essential that you find out how to provide your pet with a proper diet. Therefore, with a bit of research, and the help of a veterinarian, the task of finding a good diet for your dog will be a lot easier. In today’s article, you’ll find out about whether dogs can eat onion and what effect it can have on them.

Can dogs eat onion?

The onion or allium cepa is a vegetable that’s part of the genus Allium, which also includes vegetables such as garlic and chives. This product is very common in our diets, and has significant amounts of potassium, calcium, and vitamins that can really benefit us.

However, this vegetable also has a sulfuric compound called thiosulfate which, despite not being harmful to people, is highly toxic to dogs. So, allowing your dog to eat onion can be dangerous, regardless of whether you feed it raw, cooked, or dehydrated.

A cut onion on a table.

Why can’t dogs eat onion?

Onions are toxic foods for dogs, as canines don’t have the necessary enzymes to digest the sulfuric compound of this vegetable. Therefore, it’s advisable to replace this food with another that provides the necessary vitamins and nutrients to the animal without running the risk of serious health problems.

How many onions be harmful?

According to the European Federation of Pet Food Manufacturers, consuming a certain amount of onion leads to oxidative damage to the lipid membrane of red blood cells in dogs. It also results in the irreversible oxidative denaturation of hemoglobin, causing anemia problems in dogs.

Maybe your dog has occasionally ingested a small piece of onion, or maybe some food you made for them contained it. Although it may contradict what we’ve already told you, it’s unlikely that the dog had any problems. So, how much onion is harmful for a dog?

Well, onion is a dangerous food for canines when given in large doses or in small repetitive portions. More specifically, a dog can be poisoned if it consumes 0.5% of its weight in onion. In other words, if a 40-kilo dog eats 200 grams of onion, it will be in danger.

Symptoms of onion poisoning in dogs

Although your dog is unlikely to have had health problems from having eaten a little onion at some time, it’s recommended that you never allow your dog to consume this vegetable. In this sense, if you have ever included onion in any food in your dog’s diet, try not to do it anymore.

However, if you think your dog has consumed a considerable amount of onion, look out for the following symptoms:

  • Vomiting
  • Diarrhea
  • Decreased appetite
  • Increased salivation
  • Increased pulse and respiratory rate
  • Weakness and fatigue
  • Abdominal pain
  • Pale mucous membranes

Diseases generated in dogs by the consumption of onion

This vegetable of the genus Allium can destroy a dog’s red blood cells and cause serious health problems, affecting its quality of life. The following are some of the diseases that could occur in dogs due to the presence of thiosulfate in their diet:

  • Hemolytic anemia: This pathology occurs when there’s an acceleration in the normal process of decomposition of red blood cells, which causes the accumulation of bile and hemoglobin in the body. When a dog has hemolytic anemia, its blood is dark brown in color, it feels weak, and its pulse is racing.
  • Kidney failure: In this disease, the kidneys are unable to remove waste products from the blood and this causes a build-up of toxins. In this case, dogs drink and urinate more than normal, lose appetite, lose weight, and may become depressed.

What do I do if my dog eats onion?

On the other hand, symptoms after onion consumption usually appear late, that is, days after ingestion. So, if you think your dog has consumed a considerable amount of this vegetable, you don’t need to wait for symptoms to appear. Take them immediately to a veterinarian, so that they can carry out a check-up and determine the dog’s health status.

Final thoughts

In this article, we’ve set out to answer the question: can dogs eat onion? The toxicity of onion depends on the amount of thiosulfate it contains. Therefore, it’s better to leave this vegetable out of your pet’s diet and replace it with other foods that contain the necessary vitamins, minerals, proteins and nutrients.

A dog eating an onion.

Remember that not all foods eaten by humans are suitable for dogs. Consult with a veterinarian to see if the food you’re giving your pet is suitable. This is vital in order to have a healthy, happy dog at home.

  • Allium Cepa. Wikipedia. Recogido el 21 de julio de 2021:
  • Guías nutricionales para alimentos completos y complementarios para perros y gatos. Federación Europea de Fabricantes de Alimentos para Animales de Compañía. Recogido el 21 de julio de 2021 de: