Though a number of explanations have been advanced regarding rosacea (rose-AY-shah), doctors still haven't found a single, definite cause. One common theory is that it's a disorder of the vascular system, in which the blood vessels swell in reaction to some trigger. This idea is partially supported by the fact that people with rosacea often have migraines as well, and drugs which dilate blood vessels tend to make rosacea worse. Another belief is that a tiny skin mite called Demodex folliculorum (DEHM-oh-deks fahl-LIHK-you-LORE-uhm) plays a role, perhaps by clogging the facial hair follicles in which it lives. Some researchers think that the bacteria H. pylori (H pye-LOHR-ee), the same bacteria that causes ulcers, may be involved. Still others feel an autoimmune response or extreme sensitivity to triggers like heat and cold may be to blame for the development of rosacea. However, most experts think that rosacea is likely the result of several conditions that may work together. People may also inherit a tendency toward the disorder. Factors such as excess alcohol, sunlight, wind, emotional stress, hot beverages, and spicy foods can increase the symptoms of rosacea, but aren't believed to cause it.