What causes face sweating even if temperature is normal?

Excitement may cause face flushing and that may increase the temperature of the face that would cause reflex attempt of the body to cool resulting in the sweating.

Increased sweating a.k.a hyperhidrosis could have multiple causes, including anxiety, thyroid disorders, hypoglycemia, adrenal gland disorders, infections, autonomic disorders and also can be idiopathic, meaning no identifiable cause found. Consult your doctor for a focused examination and workup