The danger triangle of the face is the triangular area formed from the root of the nose to the corners of the mouth on both sides. Since the facial veins have no valves and are very superficial, if there is inflammation or infection in the danger triangle, bacteria or toxins can enter the skull along the facial veins and cause intracranial infection or meningitis. More common is cavernous sinus thrombophlebitis, which is so severe that the patient may develop a high fever, with a temperature greater than 39°C, and may die from a serious infection. Therefore, when there is inflammation and boils in the danger triangle, you should not squeeze it with your hands. This is because squeezing may cause bacteria to flow backwards through the blood vessels and serious intracranial infections may occur.