Facial sweat is a natural bodily response that helps regulate body temperature and maintain overall health. However, excessive facial sweating can be a source of concern for many individuals, leading to discomfort, embarrassment, and self-consciousness. Some causes of excessive facial sweating are:
Hyperhidrosis: Although the excessive sweating (or hyperhidrosis) mainly affects axilla, palms and soles, it could produce facial excessive sweating.  An excessive facial sweating could be produced by a dysfunction of the autonomic nervous system, resulting in neurogenic overactivity of normal sweat glands.  This will create significant emotional, physical, or social discomfort. Pharmacologic treatment with botulinum toxin type A (BTX-A) would be appropriate for patients with severe facial hyperhidrosis who experience blurred vision from sweating or severe distressed with their appearance. 
Horner’s Syndrome: Facial sweating might be a consequence of a lesion on the CNS, and the location of such lesion could be determined by the pattern of the unusual sweating. For example, in patients whose lesion is distal to the bifurcation of the common carotid artery, the impairment of sweating will be confined to the medial aspect of the forehead and side of the nose. 
Gustatory sweating: Facial sweating during eating (gustatory sweating) has been observed in patients with diabetes and is considered to be a feature of autonomic neuropathy. 5 A similar symptom is a sequela from trauma in the parotid glands, producing Frey’s Syndrome. 
Headache: Sweating and vascular responses in the face could be part of the symptoms of some primary headache conditions, such as migraine and cluster headaches. This is secondary to the participation of the autonomic system in the pain mechanism and is usually self-limiting.
Harlequin syndrome: This is a rare disorder of the sympathetic nervous system in which sweating and flushing of the skin are caused by unilateral blockade of sympathetic fibers, which carry the vasodilator and sudomotor nerves to the face. it can also be a manifestation of underlying cervical and upper thoracic pathologies resulting in the compression of the sympathetic fibers.
Menopause: The common description is “Hot flashes”, and will be a rapid and exaggerated heat dissipation response, consisting of profuse sweating, peripheral vasodilation, and feelings of intense, internal heat. 
There are several reasons why a person will have excessive sweating in the face, including infections, hyperglycemia, tumors, medications, stress, and withdrawal from medications or drugs. A complete workup is required to determine the reason for the excessive sweating!
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