The area of the upper lip and the lower pa of the nose is the danger area of the face. It is due to that this area is the common site of infectionThis area is drained by facial vein which communicates with the cavernous sinus through the superior ophthalmic vein and pterygoid venous plexus through the emissary veinIn case of any infection of this area, it may spread to the cavernous sinus causing infection and/or thrombosisRef: PL Dhingra, Diseases of Ear, Nose & Throat, 7th edition, pg no. 225 - 226