What is Frey's Syndrome? Frey's Syndrome is a syndrome that includes sweating while eating (gustatory sweating) and facial flushing. It is caused by injury to a nerve, called the auriculotemporal nerve, typically after surgical trauma to the parotid gland Frey's syndrome is thought to be caused by damage to both the nerves that regulate the sweat glands, and the nerves that regulate the parotid glands. It is believed that the damaged nerves regrow abnormally and connect to the wrong glands.