A veterinarian reveals if cancer could cause a cat’s vomit to be white and foaming.

If your cat has been retching a foamy white substance lately, perhaps you’ve wondered if this could mean cancer.

But there are actually many non-cancer causes of white, frothy vomitus, including overeating and, interestingly, not eating enough.

“Unfortunately, any one of about a zillion things” could be responsible, begins Jean Hofve, DVM, who has 20+ years’ experience in both conventional and alternative veterinary medicine, and author of the eBook, “What Cats Should Eat.

Dr. Hofve continues, “There are more differentials (potential causes) for vomiting than for just about any other symptom, especially in cats!”


“There are hundreds of causes [of specifically a foamy white caliber to the vomitus], and yes, cancer CAN be one of them,” explains Dr. Hofve.

“Cancer, IBD, neurological problems, etc., in the early stages can in fact produce mild, intermittent symptoms, like white foamy vomit.”

She adds, “What’s in the vomit depends on what’s in the stomach, and that can be anything from a pile of food to a little bit of foam.”

Before you jump to the conclusion that your cat’s second day of upchucking a sudsy-looking substance means your pet has cancer, there are other considerations to take note of.

Dr. Hofve notes that “if other symptoms arise, or, if it gets worse (more frequent, more severe, etc.), then the chances of serious disease go up.

If the cat hasn’t eaten lately, then the vomit will be only foam, regardless of the cause of the vomiting.

“The key is really that a mild bout of vomiting, by itself, isn’t an issue. If it’s cancer, it will eventually get worse.

“The important thing to know is that occasional, minor instances of vomiting are not usually significant as long as the cat is acting normal (no changes in eating, drinking, peeing, pooping or behavior).

“One thing I see frequently is a cat vomiting clear foamy mucus after eating grass. It may take a few tries to get out the grass itself. The same thing often happens with hairballs: multiple efforts that produce only foam, before the piece de resistance is finally ejected.”

When should you take your cat to the vet?

Dr. Hofve says, “If the vomiting persists; becomes more frequent; changes character; or additional symptoms (poor appetite, lethargy, fever, diarrhea, etc.) develop then it’s time to visit the vet.”

Other Medical Conditions that Can Cause a Cat to Throw up White Foam

Inflammatory bowel disease (IBD); inflammation of the small intestine; and disease of the liver, thyroid and kidney.

But if your cat has one of these conditions, chances are pretty good that there will be other symptoms like diarrhea and lethargy.

And more specifically, cancer of the GI tract and brain can result in a cat vomiting up some white foam.

Now retired from veterinary medicine, Dr. Hofve has researched pet nutrition and the pet food industry since the early 1990s. She has written dozens of articles and has been interviewed for print, radio and television around the world.
Lorra Garrick has been covering medical, fitness and cybersecurity topics for many years, having written thousands of articles for print magazines and websites, including as a ghostwriter. She’s also a former ACE-certified personal trainer.