“Harlequin sign” might sound like a fun card game or a Halloween outfit, but it’s actually a rare nervous system condition characterized by asymmetrical sweating. Sydney Patrice (pictured below), a physical therapist from Boston, explained that only half of her face turns red and sweats when she exercises, while the other side stays ghostly pale and completely dry. Neurosurgeon Dr. Betsy Grunch explained that if you’re stressed out, your eyes get really big, your face gets flushed, you sweat, and your mouth gets dry. “That’s all part of your body’s fight or flight mechanism, and it travels through the sympathetic chain, which lies in front of the spine.” She went on to explain that when that chain gets damaged, it can cause Harlequin syndrome. Why only one side? “Because you have a sympathetic chain on either side and each supplies one side of your face,” Dr. Grunch noted. Though exact numbers are difficult to pin down, Harlequin syndrome is estimated to affect fewer than 1,000 people in the U.S. It’s generally a temporary and benign condition, but symptoms can become permanent in some situations.
