Swallowing a small amount of blood is considered harmless, but swallowing a large amount can cause illness and vomiting, states HealthTap. Hemophilia of Georgia states that swallowed blood can stick to the lining of the stomach and also cause sickness.
Once blood is swallowed, the stomach breaks it down and digests it before transferring it to the intestinal tract, states HealthTap. If too much is consumed, it can have a laxative effect on the intestines and cause loose stools with a maroon or black color. Those who suffer from hemophilia have constant mouth bleeds that cause them to swallow more blood than is usual, notes Hemophilia of Georgia. However, they don't create any major emergencies from ingesting blood, and they are typically given blood-clotting medicine or do-it-yourself remedies to prevent blood ingestion.