Limited studies have suggested that a bacterium commonly associated with peptic ulcers and other gastric disorders, called Helicobacter pylori, may play a role in triggering rosacea in some patients.

Evidence of H. pylori was found in 19 of 20 rosacea patients in one study and in 26 of 31 rosacea patients in another, according to Dr. Richard B. Odom, chairman of dermatology at the University of California at San Francisco.

He noted, however, that a third study showed no difference in the presence of H. pylori between rosacea patients and those without the condition.

How might H. pylori affect rosacea? The association is unclear, as the bacterium has also been found in up to 80 percent of all individuals over 50.

"It's possible there is a vascular link," Dr. Odom said. "H. pylori synthesizes gastrin, a hormone that causes flushing, so it makes sense to add it to the list of potential flare-up triggers in those who already have rosacea."

Some common tripwires for rosacea flare-ups in various individuals -- which may be linked to flushing -- include sun, stress, hot weather, exercise, hot baths, spicy foods, alcohol, hot beverages, strong winds, cold weather and various others.