What causes rosacea isn't known. The ongoing skin changes may be caused by problems with the immune system or issues with blood vessels. Or the changes may be a reaction to microorganisms on the skin or ultraviolet (UV) light exposure. And genetics may be involved, as rosacea seems to run in families.

People with rosacea may have:

• Sensitive, dry skin on the face that may burn or sting.
• A flushed, red face in people with lighter skin. In those with darker skin, there can be dusky brown areas or yellowish-brown bumps.
• Small bumps and pimples or acne-like breakouts.
• Skin that gets coarser and thicker, with a bumpy texture.
• Dry, red, irritated eyes.

In rare cases, rosacea that is not treated may cause lasting effects. These include loss of vision and thickened skin that makes bumps on the nose, called rhinophyma (say "ry-no-FY-muh"). But most cases of rosacea don't progress this far.

In a person with lighter skin, rosacea is usually diagnosed by the pattern of redness on the face. But in a person with darker skin, redness may not show. Symptoms such as skin on the face that stings or burns or has small bumps can help with diagnosis. Medical tests are not usually needed.