New medical research into the process of facial flushing and redness has found that individuals with rosacea register greater nerve, blood vessel and sweating responses than people without the disorder when exposed to increased heat or stress. Results of the National Rosacea Society-funded study also uncovered a role for the autonomic nervous system, which helps operate key functions of the body without conscious control.

"Heat and stress have long been recognized as rosacea triggers, but it has not been clear what happens in the body when these flare-ups occur," said Dr. Thad Wilson, associate professor of physiology at Ohio University. "That's why we devised innovative ways to replicate these triggers in a controlled manner while studying their effects on nerves, blood flow and sweating."

To increase body temperature, the researchers had 10 rosacea patients and 10 normal individuals wear a tight-fitting suit lined with tubes carrying water heated to 114.8°F until their body temperature increased by approximately 2°F. Each person was then precisely measured for nerve activity, forehead skin blood flow and forehead sweat rate.

The researchers found that rosacea patients had higher blood flow and sweating rates compared to normal subjects both before and after the heating began, and their blood flow and sweating also began to increase more rapidly during heating.

In a separate part of the study, heart rate, nerve activity and blood pressure were monitored in 12 rosacea patients and 12 normal subjects during mental and physical tests. These included performing mental subtraction exercises for two minutes, using hand gestures to indicate answers, and squeezing a handgrip for two minutes.

While heart rate and blood pressure were the same between the groups during the hand exercises, blood flow was higher during mental arithmetic in the rosacea patients. The rosacea patients also experienced heightened nerve activity compared to those without rosacea during both the mental and physical portions of the test.

"These results indicate that rosacea symptoms may be in part due to nerve overactivity," Dr. Wilson said. "This is an important area that warrants further investigation, as it may lead to improvements in therapy."

The greater responses in rosacea patients occurred in the sympathetic nervous system, a part of the body's autonomic nervous system that controls involuntary functions such as heart rate, digestion, breathing and perspiration. This portion of the autonomic nervous system functions largely below the level of consciousness and has been shown to respond to emotion.