What Should You Do If Your Cat Ate Onion?

Onion is usually at the top of the list of foods that should never be given to your cat, not even by mistake, and for good reason.

Unlike butter or raw chicken, which may upset your cat’s stomach under certain circumstances, onions are always dangerous for cats.

If your cat ate onion, you should call your veterinarian immediately and get advice.

It is not always an emergency, but symptoms of onion toxicity may show up days after ingestion and by then it might be too late to intervene.

What should you do if your cat eats an onion?

As soon as you realize that your cat ate a little bit of onion, you should call your veterinarian and explain the situation.

If it’s after hours, call the nearest emergency clinic or the Pet Poison Helpline.

Be prepared to answer a few questions, such as:

  • How much onion did your cat eat approximately?
  • What kind of onion did they eat? (Ex: cat ate green onions, red onions, raw, cooked, dehydrated onions, onion powder, etc)
  • How long ago do you think they ate it?
  • Is your cat showing any symptoms?

Onions are toxic to cats, so unless your cat ingested a very small amount or there are other circumstances that might push your veterinarian to suggest home treatment, you will be asked to bring your pet in for an examination.

Not all cats will feel sick from eating onion, however, the outcome of onion ingestion in cats is so uncertain that it is not safe to wait for symptoms to show up because it might be too late for treatments.

Sometimes the cat will need to be hospitalized until they’re out of danger because onion toxicity has a slow course of action. In fact, the cat might feel sick 5-7 days after ingesting onion.

What not to do if your cat eats an onion?

Many pet parents know that onions are toxic to cats and may want to make their cat throw up the food as soon as possible, for fear of worse consequences.

Of course, it’s not easy to manage such a dangerous situation, however, acting without consulting a veterinarian might put your cat’s life at risk.

When dogs eat dangerous items, it is common practice to induce vomiting within 2 hours from ingestion. However, cats are often immune to this procedure so don’t try to induce vomiting in your cat.

The procedure is a dangerous one to do at home and it shouldn’t be done without previous experience. The veterinarian may choose to induce vomiting in your cat, but most often they might use activated charcoal instead.

Activated charcoal is often used in cases of intoxication, because it’s a harmless substance that can protect and absorb the toxins from the gastrointestinal tract before it has the time to spread through the body, poisoning the bloodstream and reaching the organs.

Why are onions bad for cats?

Onions are toxic for many animals, including dogs and horses. However, cats are more affected by onion toxicity, in fact, even a bite of any part of the onion can affect your cat. When ingested, onions cause hemolysis in cats.

Hemolysis, also called hemolytic anemia or Heinz body anemia is a condition where the red blood cells that carry oxygen start to break down.

As fewer and fewer cells circulate in the bloodstream, organs have less oxygen to work with, which results in weakness, panting, and if not treated in time, death.

Cats have a strong adverse reaction to the oxidant n-propyl disulfide present in onions.

It is present in all types of onions, and its effect is particularly strong if a cat ingests onion powder. That doesn’t mean that if your cat ate cooked onions or raw onions the situation is any less dangerous, of course.

The body identifies this oxidant as a harmful substance and since n-propyl disulfide is attached to the red blood cells and cannot be removed, the body reacts by destroying the cells in an attempt to get rid of the invader.

Diagnosis of onion poisoning in cats 

When cats eat onions, the toxic effects are often delayed for days, which makes onions very dangerous because if you do not realize that your cat has eaten onions, when your pet starts showing symptoms it might be too late.

Onion poisoning provokes symptoms similar to an allergic reaction, so when it looks like cats are allergic to onions, they may actually be intoxicated.

Symptoms of onion toxicity in cats include:

  • Weakness
  • Increased heart rate
  • Panting
  • Vomiting
  • Asthma
  • Gastrointestinal issues
  • Blood in the urine
  • Allergic reaction
  • Diarrhea
  • Liver damage
  • Fainting
  • Lethargy
  • Lack of appetite
  • Contact dermatitis

The diagnosis can only be made by a professional after examining your cat’s medical history and diet. A blood sample will be taken in order to confirm the diagnosis of hemolytic anemia.

However, hemolytic anemia can be the symptom of different feline diseases, so if you and your veterinarian suspect onion poisoning, radiographs and a biochemistry profile will probably be required.

Treatment of onion poisoning in cats 

There is no medicine or specific treatment that will heal cats from onion poisoning, that’s why it’s fundamental that they get medical assistance as soon as possible.

The only treatment available for onion toxicity is supportive care, for which the cat may need to stay in the hospital for a few days, so they can be monitored and supplied with intravenous fluids therapy.

Fluid therapy is needed to flush the body from the toxins so that it can stop destroying its blood-red cells in the attempt of getting rid of the foreign substance.

Usually, after the cat stops ingesting the toxin, their bone marrow starts producing new blood red cells to substitute those lost. However, if your cat suffered a great loss of blood, a transfusion of blood may be needed.

Once the cat has been treated, it should start recovering immediately. Depending on their original conditions, they should start feeling better within a few hours, or the day after.

After recovery, the veterinarian may choose to run more tests to check the functionality of the organs. If blood transfusion was required during treatment, a follow-up appointment may be needed.

As evidenced by the numerous procedures required, onion poisoning can become a very expensive issue. Treatment may cost anywhere between 500-4000$.

After your cat is back home, you can help their recovery by feeding them fresh chicken, meat, or fish with every meal. A wet food-only diet is also recommended because it will go easy on the GI tract.

How much onion will hurt a cat?

Onions are poisonous to cats even in small amounts, although there is a debate on how much onion will hurt a cat.

Usually, 5 g of onion per kilogram (2.2 pounds) of body weight is considered toxic, but it can be as low as 1 g per 2 kilograms (4.4 pounds) of body weight.

It is safe to say that there is no safe amount of onion for cats. Even if the onion is just one of the ingredients (like in baby food), a cat might get sick from ingesting it.

Moreover, even if your cat eats a little amount of onion and doesn’t get sick, it doesn’t mean they’re out of danger, because onion toxicity is accumulative.

This means that if a cat happens to eat onions repeatedly, they might not get sick the first time but they will become intoxicated, eventually.

Can cats eat onions? 

Cats and onions should not interact. Onions are among the most toxic foods for cats and there is no safe amount of onion that a cat can ingest.

While a small amount of onion might not hurt your cat, there is no guarantee they won’t become intoxicated days later. Usually, when cats start showing symptoms of onion poisoning, the situation is already serious, and it might become lethal.

That’s why it’s important to contact the veterinarian right away when your cat eats onion. Onions contain a toxin that provokes severe anemia in cats, which requires numerous exams and, often, hospitalization for intravenous fluids treatment.

Onion ingestion can be deadly for your pet, and when it’s not it translates into expensive medical treatment. That’s why it’s safer (and cheaper) to take all necessary precautions in order to keep onions away from your cat.

Can cats eat raw onions? 

Raw onions are actually more dangerous than cooked onions, because the cooking process ‘weakens’ the onion and its properties, although cooked onions remain extremely poisonous for cats.

Onions in their raw form are present in many dishes and fast food we eat every day, so it’s fundamental that you never leave leftovers where your cat can reach.

Cats don’t like onions, but are often attracted by the smell of other ingredients we cook onions with, that’s why even if the onion is all that’s left on the plate, they might eat it.

Can cats eat onion powder? 

Onion powder is famous for its concentrated onion flavor, however, it also means it’s more powerful than fresh onion and therefore more dangerous.

Among all types of onion, onion powder is in fact the most toxic for cats and the most problematic, because onion powder is often a hidden ingredient and you may not be aware that your cat is eating onion powder.

Onion powder might be present even in unsuspected foods. In “A Guide to Poisonous House and Garden Plants” veterinarian, Anthony Knight reports a case of onion poisoning in a cat because of baby food that contained only 0.3 percent of onion powder.

It is clear that onion is poisonous to cats in every form. No matter the amount ingested, consulting your veterinarian and getting prompt medical assistance can save your cat’s life.

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