The National Rosacea Society Expert Committee on the Classification and Staging of Rosacea identified four types of rosacea (Source: Journal of the American Academy of Dermatology, April 2002, pages 584-587):
Papulopustular: Papules and pustules are often seen, with persistent facial redness and some swelling.
Phymatous: Thickening of the skin occurs with enlarged pores and surface nodules, and often rhinophyma is present.
Erythematotelangiectatic: Flushing and persistent redness is present with visible blood vessels (telangiectasias), along with swelling, stinging, and burning along the cheeks, chin, and forehead. The skin can also be dry.
Ocular: The white part of the eye (sclera) has a persistent sensation of burning, grittiness, dryness, and a feeling that something is in the eye, with visible blood vessels. Often sties, blepharitis (inflammation of the eyelid), and conjunctivitis (pink eye) are present and recurring. Most eye makeup increases this irritation to the point where it becomes very uncomfortable.
what causes rosacea?
Surprisingly, no one really knows what causes rosacea, but theories do exist and there those who champion one over the other. UV light is thought to be a culprit for causing rosacea. A genetic propensity for producing capillaries (angiogenesis) is another. There is also research suggesting that the vitamin D3 pathway may be deficient, creating an environment where rosacea symptoms can manifest more easily.
(Sources: Experimental Dermatology, August 2008, pages 633-699; Cosmetic Dermatology, April 2008, pages 224-232; Archives of Dermatological Research, March 2008, pages 125-131; and Journal of Dermatological Treatment, 2007, volume 18, issue 6, pages 326-328.)
One of the more popular theories being debated is whether the presence of a mite called De- modexfolliculorum that is present in skin is responsible for the inflammatory aspect of rosacea. There is some evidence that this mite, which thrives on a large percentage of people, especially older people, is more prevalent in those with rosacea. But the research is hardly conclusive. (Sources: British Journal of Dermatology, September 2007, pages 474-481; Cutis, September 2004, pages S9-S12; and Acta Dermato-Venereologica, January 2002, pages 3-6.)
Other research indicates that unidentified and unknown microbes are creating the inflammatory response and other symptoms seen in rosacea. But whether it is an unknown microbe under the skin or the Demodex folliculorum mite, research shows that the active ingredient metronidazole may work to control the situation. Since it can kill both the mite and other microbes, you would be covering both issues with one medication. (Sources: Journal of Drugs in Dermatology, May 2007, pages 495-498; and Advances in Therapy, September-October 2001, pages 237-243.)
Despite the fact that a clear understanding of why rosacea happens is lacking, many cosmetics companies want you to believe their skin-care products can control different aspects of the disorder, especially with respect to the mite mentioned above. But there is no research showing that over-the-counter products control any aspect of rosacea other than mitigating redness and inflammation and not making it worse.
What this all adds up to is that no one answer is right or wrong. We simply don’t know what is actually taking place, although it seems to be a complex interplay between physiological events taking place in the skin and how it responds to external influences. What is certain, regardless of the cause, is that if they are left untreated, rosacea symptoms will increase, resulting in chronic redness, swelling, breakouts, surfaced capillaries, and/or flaking skin.