Bacteria living within the mites that dwell in normal human skin may play a role in causing rosacea — a condition that turns patches of skin on the face red or bumpy, recent research suggests.

About 3 percent of people have rosacea, although the condition is more common in fair-skinned people, and those with weakened immune systems. While it doesn't affect a person's general health, it can be painful or embarrassing, said Kevin Kavanagh, of the National University of Ireland, Maynooth.

Kavanagh and colleagues reviewed recent evidence showing rosacea may be triggered by bacteria that live within tiny mites on the skin.

Mites of a species called Demodex folliculorum live harmlessly in normal skin, dwelling inside structures surrounding hair follicles. Research now shows rosacea patients have more of these mites in their skin than those without rosacea, Kavanagh said.

The mites are known to contain bacteria called Bacillus oleronius, which produce a protein that provokes an immune reaction in rosacea patients. The research suggests this is what may trigger the condition, Kavanagh said.

Moreover, these bacteria are sensitive to the antibiotics used to treat rosacea. (Antibiotics have been used to treat rosacea, but mainly for their anti-inflammatory effects, not because they kill bacteria.)

"When the mites die, the bacteria are released and leak into surrounding skin tissues — triggering tissue degradation and inflammation," Kavanagh said.

"Targeting these bacteria may be a useful way of treating and preventing this condition," Kavanagh said. Kavanagh also noted some pharmaceutical companies are already developing therapies to control the population of mites in the face of patients.

Kavanagh's review was published Aug. 29 in the Journal of Medical Microbiology.