What is hairball in cats
A hairball is a mass of fur in a cat's stomach that is vomited when too large, often mistaken for tumors or other serious gastrointestinal conditions.
A hairball is a mass of packed fur formed in the stomach that is occasionally vomited up when it becomes too large. While common in cats due to their grooming habits, these trichobezoars can be mistaken for serious conditions like lymphosarcoma or tumors, and in extreme cases require surgical intervention.
How hairballs form in the stomach
A hairball, technically known as a trichobezoar, is a tight elongated cylinder of packed fur that accumulates in the gastrointestinal system. Cats are especially prone to this because they groom themselves by licking their fur, thereby ingesting it. The mass may also include bits of swallowed food, but the primary component is hair that has passed through the esophagus and collected in the stomach.
The cat's tongue is the mechanism that drives this process. The dorsal aspect of the tongue is covered in 5 types of sharp spines, or papillae, which allow the cat to effectively groom itself. These spines act like a comb, catching loose hair and pulling it into the mouth. While the digestive system can usually handle small amounts of hair, the accumulation eventually forms a mass that the stomach cannot pass into the intestines.
Why cats are different from other animals
Cats are unique in their ability to regurgitate these masses, a trait that distinguishes them from other animals that accumulate hair. Rabbits are also prone to hairball formation because they groom themselves in the same fashion as cats, but they cannot regurgitate them. Due to the fragility of their digestive systems, hairballs in rabbits must be treated immediately or they may stop feeding and ultimately die from dehydration.
Cattle are also known to accumulate hairballs, but as they do not vomit, these are found usually after death and can be quite large. In humans, hairballs are uncommon and occur when hair strands collect in the stomach and are unable to be ejected due to not enough friction with the surface of the gastric mucosa. This can result in the general impairment of the digestive system, as hair cannot be digested or passed by the human gastrointestinal system.
When a hairball is a medical emergency
Animals with hairballs are sometimes mistaken as having other conditions of the stomach such as lymphosarcoma, tuberculosis, and tumor of the spleen. A trichobezoar is a bezoar formed from the ingestion of hair, and while often associated with trichotillomania in humans, in cats it is a mechanical issue. Trichobezoars are rare in a clinical sense but can be fatal if undetected.
Surgical intervention is often required if the mass becomes too large to pass naturally. Persistent vomiting warrants clinical evaluation to rule out gastrointestinal disease, as the behavior is not always benign. A 2025 microscopy study of regurgitated matter found leaf trichomes interlocked with hair, suggesting that plant fibers may help pass hairballs, yet pet cat owners in surveys have not observed behavioral changes to support this hypothesis as a reliable cure.
The role of fiber and plant matter
Many owners use cat grass, a colloquial term for trays or pots of young cereal grasses, to aid the passing of hairballs. Cat grass typically comprises wheatgrass, barley grass, oat grass, and/or rye, sown densely and presented at the sprout/microgreen stage. These cereal grasses are rich in fiber, including soluble fractions, chlorophyll, and water-soluble vitamins.
Cats are believed to consume grasses primarily for their fiber content. In this regard, cat grass supplants nibbling on houseplants or lawn grasses. Cats may use plant fibers to help pass hairballs, as the rough texture of the grass can stimulate the vomiting reflex or aid in moving the mass through the gut. However, this is a management strategy rather than a guaranteed prevention method.
Recognizing the signs
The most obvious sign of a hairball is the occasional vomiting of a cylindrical mass of fur. However, owners should not assume every instance of vomiting is a hairball. If a cat is persistently vomiting, it requires clinical evaluation to rule out gastrointestinal disease. The presence of a hairball is a normal physiological event for many cats, but the frequency and severity of the vomiting can indicate an underlying issue.
Understanding the anatomy helps explain why this happens. The cat's stomach is designed to handle a large meal, and the primordial pouch provides extra room for the stomach to expand. This allows the cat to bend and expand, but it does not prevent the accumulation of hair that exceeds the stomach's ability to move it forward. When the mass becomes too big, the body's natural defense is to expel it.