You heal more slowly.
A little stress can be good for your body, keeping you mentally sharp and focused. But too much can wear on your immune system, making you more susceptible to skin infections, like cold sores, says New York City dermatologist Sumayah Jamal
, MD, of Schweiger Dermatology Group. What's more, excessive stress could make it take you longer to rebound. "Stress delays the skin's healing process by impairing the barrier function, or protective outer layer," says Josie Howard
, MD, a San Francisco psychiatrist who specializes in psycho-dermatology. In fact, in a small study
analyzing the skin of medical students during exams and then after vacation, researchers found that "wound healing was significantly delayed" during finals, says Howard.