The danger area of the face
Upper lip and the lower part of nose area is called dangerous area of face. The facial vein communicates with the cavernous sinus through the deep facial vein with the pterygoid venous plexus which passes backward over the buccinator.
Excessive irritation or aggravation of infected tissues, whose venous drainage is connected to the cavernous sinus, may result in a spread of infection to the cavernous sinus and then to the brain. For this reason, particular caution should be used to avoid needless aggravation of infected tissue in these areas. This venous drainage pattern is of particular importance since the veins of the face contain no valves as do veins in other parts of the body.