Theories On What Causes Rosacea?

The exact cause of rosacea is unknown. One theory is that some people have blood vessels that are easily irritated. Another possible cause is tiny mites that normally live on our skin. People with rosacea have more of these mites on their faces than those who don't have the disease.
Pimples may result when a flare-up of rosacea heats the skin, causing bacteria to grow. Flare-ups often start when certain triggers cause the blood vessels in the face to dilate, or expand, which causes redness. Common triggers are exercise, hot weather, stress, spicy foods, alcohol, and hot baths. Swings in temperature from hot to cold or cold to hot can also trigger a flare of rosacea.