How does infection cause a blood clot to occur?
Any infection on your face, such as infection from a pimple or boil in the nostril or on the upper lip or nose, may cause inflammation (swelling) in that area. This is called cellulitis (see Useful links for more information about cellulitis). From this inflammation, infection may spread to one of the cavernous sinuses. If this happens, the blood in the sinus may turn into an infected clot (see Causes, above).
