Facial hyperhidrosis, otherwise recognized as excessive facial sweating. Excessive facial sweating and facial blushing usually occurs during mild social situations that would not normally cause these conditions. It usually starts after puberty. Facial hyperhidrosis is caused by a hyperactive sympathetic nervous system, which is located in the chest cavity. Sympathetic facial blushing caused by hyperhidrosis differs from rosacea, another condition that causes facial redness.