Cats are wonderful creatures with whom to share our homes and lives. They entertain, comfort and sooth. While cats, like Mary Poppins, are practically perfect in every way, they do have one annoying habit: vomiting up hairballs.

Cats never seem to vomit a hairball neatly in the corner. Instead, they always choose the exact spot you’re most likely to step on it—soggy, squishy and simply revolting.

So why does your cat vomit hairballs? And when might hairballs indicate a medical condition? Let’s take a closer look at what’s new in our understanding of feline hairballs.

How do hairballs form?

A cat’s tongue serves as a grooming tool for their fur. The backward-facing barbs on your cat’s tongue act just like you comb or brush, trapping loose fur during grooming. Given their fastidious nature, cats end up swallowing a large amount of fur daily.

Normally, the hair passes through the intestinal tract and out of the body in the feces. In some cats, the hair accumulates in a large wad in the stomach or intestine.

We call the accumulation of hair a trichobezoar— “tricho” is Greek for hair and “bezoar” is thought to be Arabic or Persian and historically referred to substances believed to protect against poison.

When are hairballs a sign of disease?

Occasional hairballs are common and usually harmless. However, frequent hairballs or hairball-related intestinal blockages can indicate an underlying medical problem.

In one study of a series of cats with intestinal blockage due to a hairball, the cats had illnesses or risk factors that either increased hair ingestion or interfered with normal intestinal movement. These included:

Long hair coats

Itchy skin from fleas

Inflammatory bowel disease (IBD)

Ingestion of undigestible plant material

An association was also found between hairball obstruction and intestinal lymphoma. This information suggests that if your cat needs surgery to remove a hairball, an intestinal biopsy should also be performed at the same time. Identifying an underlying disease can be critical to preventing future obstructions.

Does eating plants help hairballs pass?

Many cat owners offer “cat grass” believing it helps hairballs pass more easily—but is this true?

Historically, consumption of undigestible plant material has been associated with hairball development. One study found that long- and short-haired cats ate plants with equal frequency, leading the authors to conclude long-haired cats have not evolved to eat plants as a protective mechanism against hairballs.

However, newer research adds nuance to this belief.

A recent study used electron microscopy to analyze the plant matter in hairballs and concluded that feeding cat grass has a scientific basis for helping hairballs pass. The researchers found that certain plant structure—such as serrated edges and tiny epidermal hairs—can physically snag the hair and help it along the intestinal tract, much like a “snake” pulls hair out of your shower drain.

Should you give your cat grass?

While some cats may benefit from cat grass, it is not appropriate for every feline. If cat grass causes significant vomiting or a loss of appetite, restrict your cat’s access to the plants.

If your cat has an uptick in hairball production, check in with your veterinarian and make sure there is not a medical issue that needs to be addressed.

The Bottom Line on Hairballs in Cats

Occasional hairballs are normal

Frequent or severe hairballs are not normal

Underlying skin or gastrointestinal disease should always be considered with abnormal hairball production

New research suggests cat grass may help some cats—but it’s not a cure-all

When in doubt, your veterinarian can help determine whether your cat’s hairballs are a nuisance—or a sign of something more serious.