White, foamy vomit is common when a cat vomits on an empty stomach. Your cat’s stomach contains a small amount of fluid and mucus between meals, and this fluid and mucus results in white, foamy vomit.

Vomiting white foam can be a sign that your cat’s stomach is empty, or it could indicate inflammation or an obstruction in the gastrointestinal tract.

Vomiting white foam may be a sign that your cat is trying to expel a hairball.” Another potential cause of a cat vomiting white foam is gastritis, which is inflammation of the stomach lining.