 Frey's syndrome often results as a side effect of surgeries of or near the parotid gland or due to injury to the auriculotemporal nerve, which passes through the parotid gland in the early part of its course.The auriculotemporal branch of the mandibular (V3) branch of the trigeminal nerve carries parasympathetic fibers to the parotid salivary gland and sympathetic fibers to the sweat glands of the scalp.As a result of severance and inappropriate regeneration, the parasympathetic nerve fibers may switch course to a sympathetic response, resulting in "gustatory sweating" or sweating in the anticipation of eating, instead of the normal salivatory response.