Dangerous triangle Definition: The area from the root of the nose to the corners of the mouth on both sides Characteristics of this area: The face is rich in blood circulation. The nasolabial veins often have no valves. There are many interconnected underlying fascial gaps around the face and jaws with loose cellular connective tissue, forming easy channels for infection to spread. Infections occurring in this area are susceptible to intracranial spread. Special Note: When inflammation or acne occurs in this area, avoid squeezing as much as possible to prevent the infection from spreading intracranially and causing serious consequences.