According to FelineCRF.org, vomiting white foam may indicate that a cat is suffering from an excess of stomach acid. The foamy vomit may be clear or white. Foamy vomit is sometimes an early indication that a cat is developing kidney disease, especially when it occurs soon after drinking water.
VCA Animal Hospital states that some vomiting is normal for cats. Cats groom themselves regularly, and it is hard for them to digest the hair that is swallowed in the grooming process. If a cat's vomit contains hair, it is likely to be healthy vomit and not an indication that the cat is suffering from disease. Owners should not be alarmed by the occasional episode of vomiting, foamy or otherwise, unless the vomit contains blood.
Acute vomiting episodes, in which vomiting is experienced for several days but not otherwise, can indicate a number of illnesses and ailments in cats. Many cases respond well to symptomatic treatment, which involves giving the cat moist foods to increase fluid intake and prevent dehydration. Some veterinarians also prescribe medications to control vomiting or relieve inflammation when cats are experiencing acute vomiting. If the cat does not respond to these treatments, additional tests, such as an endoscopy, X-ray or blood test, may be performed. The results of these tests are then used to look for more serious causes of acute vomiting, such as intestinal blockages or the presence of foreign bodies in the digestive tract.