WASHINGTON (June 25, 2001) -- The greater warmth of the facial skin of rosacea sufferers may play a role in triggering the unsightly papules (bumps) and pustules (pimples) often associated with this conspicuous facial disorder now estimated to affect 14 million Americans, according to a study funded by a grant from the National Rosacea Society and reported at the annual meeting of the Society for Investigative Dermatology here.

In the new study, Dr. Mark Dahl, chairman, Department of Dermatology, Mayo Clinic Scottsdale, and Dr. Patrick Schlievert, professor, Department of Microbiology, University of Minnesota, found that bacteria from the facial skin of both rosacea patients and unaffected control subjects produced substantially more toxin when at higher temperature. The study noted that the surface temperature of facial skin in rosacea patients is warmer than normal skin due to erythema (redness) and flushing.

"Researchers have long wondered whether bacteria may be responsible for the inflammation, papules and pustules of rosacea, especially because they can be successfully treated with oral and topical antibiotics," Dr. Dahl said. "Our findings suggest that temperature may change the toxicity of many types of common bacteria, opening a whole new avenue of research into this widespread but poorly understood disorder."

Drs. Dahl and Schlievert cultured samples of Staphylococcus bacteria from the pustules of four untreated rosacea patients and the skin surface of four healthy controls at both 30 and 37 degrees Celsius (86 and 99 degrees Fahrenheit). They found that, while the bacteria samples grew at the same rate at both the lower and higher temperatures, at higher temperatures the samples produced larger amounts of potentially toxic proteins.

In addition, some proteins were secreted by the bacteria at the higher temperature that were not secreted at the lower one. One such protein was analyzed and found to be a lipase that could break down oils on the skin surface. Moreover, while all samples from rosacea patients produced the lipase, half of the samples from control subjects did not.

Dr. Dahl described several possible interpretations of these study results. Common bacteria may have a tendency to generate more virulent proteins at the higher temperatures encountered on the faces of people with rosacea. Also, they generate different toxins at these higher temperatures. The nature of the toxins or the amounts produced could trigger papules and pustules.

Dr. Dahl further noted that he only studied staphylococci, and other bacteria might also behave differently on the warmer skin of rosacea patients. He called for further studies to pursue these possibilities.

Rosacea is a chronic, relapsing and often progressive disorder that typically develops after age 30. It usually first appears as a transient erythema on the cheeks, nose, chin or forehead that becomes more severe and persistent as the condition progresses, and telangiectasia (visible blood vessels) may appear. Left untreated, papules and pustules frequently develop, and in advanced cases there may be excess growth of tissue on the nose, a condition known as rhinophyma.

In some rosacea sufferers, the eyes may also be affected, often resulting in tearing or burning, bloodshot appearance, foreign-body sensation, styes or other ocular conditions.

The National Rosacea Society has instituted a research grants program to encourage and support scientific investigation into the potential causes and other key aspects of this prevalent disorder. Because the etiology of rosacea is unknown, a high priority is given to funding research in such areas as its pathogenesis, progression, mechanism of action, cell biology and potential genetic factors.

The National Rosacea Society is a nonprofit organization whose mission is to support rosacea research and to provide educational information on rosacea to physicians, patients and the public. For information and educational materials on rosacea, write the National Rosacea Society, 111 Lions Dr., Ste. 216, Barrington, Illinois 60010, or call its toll-free number at 1-888-NO-BLUSH. Information and materials are also available on the society's Web site at www.rosacea.org, or via e-mail at info@rosacea.org.