Unlike most other parts of the body, blood in saliva can occur for a variety of reasons and stem from many areas of the body. Bacteria, both those normally in the human body and those that are dangerous, can lead to infections and bleeding from the mouth. If there is any trauma or damage to the mouth or associated areas, this can cause bloody saliva. Certain types of cancers can lead to blood mixing with saliva. Drugs, both medicinal and narcotic, also can cause this symptom.
There are many types of bacteria; some occur in the body and are helpful, while others lead to problems and diseases. If there are any cuts inside the mouth, esophagus, intestines, nasal cavity or other areas associated with the mouth, then there can be blood in saliva. While bacteria are the most common cause, it also can result from viruses and fungi. This usually can be treated with antibiotics, but surgery may be needed in severe cases.
Trauma is perhaps one of the most common causes for blood in saliva, especially if the trauma directly affects the gums or mouth. For example, rough flossing or surgery involving the mouth will commonly lead to blood mixing with saliva. If there is trauma to the associated systems, such as being hit hard in the stomach, this also can cause blood. When blood is coming from an associated system, it can be very dangerous, because it means there is internal bleeding. Eating substances that are dangerously acidic or caustic also may cause this.
When cancer spreads, it can lead to bloody saliva. This may sometimes happen with benign cancer, but is not as common. It normally results from cancer in the mouth or lymph nodes, but it also can come from cancer in associated systems. At the same time, some of the treatments used to treat cancer also may lead to blood in the mouth.
Many drugs are used for medicinal purposes to cure diseases, but they also can lead to blood in saliva. This most commonly is from treatments for cancer, but blood thinners can cause minor oral cuts to bleed much more. If the user has an allergic reaction that affects the mouth or an associated system, this can occur. Narcotics, especially when used in abundance, also may cause blood in the mouth. This chance increases if the narcotics are known for affecting the oral cavity.