Why is my cat vomiting?

No pet parent likes to hear that sound: the hacking noise from the other room that tells you that you’re going to have a mess to clean up. When your cat starts gagging, the first thought that might go through your head is: "Oh no, what have they got themselves into now?" Cat vomiting, also known as puking, being sick or throwing up, is one of the most common concerns for pet parents.

There are many reasons why your cat might vomit, some of them more serious than others. For example, occasional vomiting may simply be down to them having scavenged something or eaten a mouse, but regular vomiting might indicate an underlying health issue. Whether you're a new or seasoned cat parent, it's important to know the reasons your cat may be vomiting and when it warrants a visit to the vet.

Common reasons for cat vomiting

The most common reasons your cat might be vomiting are:

• Hairballs

• Dietary indiscretion (eating something they shouldn’t have!)

• A food allergy or intolerance

• Inflammatory bowel disease

• Infection

• Foreign body in the intestines

• An underlying disease, such as chronic kidney disease

• Cancer

• Parasites

Let’s take a closer look at these.

Hairballs

Cats are fastidious groomers and spend hours a day tending to their coats. This means that they inevitably ingest fur. Normally this passes through the intestines without any issues and is passed in the faeces. Hairballs occur when, as the name suggests, excessive hair becomes clumped in the stomach and is vomited up. You’ll quite clearly see a clump of hair, often with mucus and fluid of various colours. Lovely!

Occasional vomiting of hairballs is nothing to worry about, but if it is frequent or distressing to your cat it needs looking into. If you have a long-haired cat, your vet may recommend food with higher fibre, which helps trap hair in the gut and drag it through the intestines. Extra grooming from you will also help.

Sometimes hairballs may be due to excessive grooming, which may be caused by stress, skin disease, allergies and/or parasites. If this is the case, your vet will recommend ways to address the cause, not necessarily the hairballs.

Dietary indiscretion

Lots of animals take the opportunity to steal tasty things that they find. If your cat raids a bin or steals some human food, they might have a one-off episode of vomiting. The same goes for eating wildlife. Some cats never have issues, but others will be sick if they eat all or part of their prey. Normally, these issues resolve on their own within a day.

Food allergy or intolerance

Some cats can become allergic or intolerant to something in their food. Allergies are often due to certain proteins, such as chicken, fish or dairy products. Intolerances may be due to anything. 

Inflammatory bowel disease

There are lots of different types and causes of inflammatory bowel disease in cats and, depending on the cause, your vet may recommend various options for treatment. Inflammatory bowel disease often comes with liver and pancreatic changes in cats, a condition called triaditis, because three organs are inflamed.

Infection

Just like food poisoning in humans, cats can get bacterial infections that cause vomiting and diarrhoea, especially if they eat something that’s off. There are also viral infections that can cause vomiting in cats, so keeping your cat’s vaccines up to date is important.

Foreign body in the intestines

The well-known adage “curiosity killed the cat” exists for a reason! Cats are very inquisitive animals and this sometimes gets them into trouble. Foreign bodies are more common in kittens and young adult cats because they are learning about the world and at their most mischievous and inquisitive. While dogs tend to get things like peach stones and socks stuck in their guts, cats usually have what are called linear foreign bodies, such as pieces of string or wool.

This is because cats love to play with things like balls of wool, and strings or thin nylon cords are often on fishing-style cat toys. Often, what happens is that your cat swallows while chewing on a piece of string, but the thread isn’t chewed off so they just keep swallowing more and more. These items don’t pass through the intestine well, and they cause the guts to bunch up like a concertina. Eventually, this causes blockage and can be life-threatening if left.

Underlying disease

Lots of diseases can cause vomiting and diarrhoea in cats. The most common one is kidney disease, which is very common in cats, especially older ones.

Cancer

Cancer of the intestines can cause vomiting, but so can tumours elsewhere. Tumours that spread may cause organ damage to the liver or pancreas, which can cause vomiting. Also, tumours that are large masses sitting near or pressing on the stomach could cause vomiting.

Parasites

Rarely, if a cat has a very high burden of worms, the sheer volume of worms in the stomach may cause vomiting. These are usually pretty obvious because you may see the worms in the vomit.