A cat sneezes blood usually because of an obstruction in the cat's nasal passage, a cold, bacterial infection, allergies or dental problems like an abscessed tooth, according to Vetinfo. Sneezing blood rarely indicates a more serious problem.
Cats typically sneeze blood when something gets caught in the animal's nasal passage, like a piece of food, blade of grass or string. While these blockages typically resolve on their own, Vetinfo advises taking the animal to a veterinarian to have the blockage removed if the sneezing continues for several hours. If your cat is exhibiting other symptoms, such as eye or nasal discharge, coughing or loss of appetite, it is likely suffering from a cold or allergies and needs to be treated with medications. It helps to check for any changes in the house that may have caused the sudden sneezing so the cat doesn't suffer in the future.
Sneezing blood is an indication of a serious condition in some cases, notes Vetinfo. It can be a symptom of a clotting disorder, anemia or high blood pressure. Usually when a serious problem causes the sneezing, a cat shows other symptoms, such as lethargy, changes in eating patterns, and bloody vomit or stool.