Cat hairballs are a natural byproduct of a cat's grooming process, and most are quite harmless. In rare cases, excessive hairballs may indicate an intestinal blockage that requires veterinary attention.
Cats are very fastidious animals, spending several hours a day licking and grooming themselves. Cat hairs are not smooth, so they catch on the cat's tongue and are subsequently swallowed. Indigestible hair usually passes harmlessly through the cat's stomach and intestines, or it can be regurgitated as an unpleasant mass. The scientific name for a hairball is “trichobezoar.”
Occasionally a cat makes retching sounds while producing no hairball. If this behavior occurs simultaneously with severe lethargy and food refusal for two or more days, a veterinarian should be consulted as the cat may be suffering from an intestinal blockage. Clinical therapies include surgery, laxatives and intravenous rehydration.