Bell’s palsy is the most common type of facial nerve paralysis, though it’s not clear what causes it. Experts think it may result from a viral infection that leaves your facial nerve inflamed. Facial muscles — usually on just one side of your face — become weak or unable to move.
With time, symptoms usually resolve, but they can be alarming, and should be evaluated quickly. Other more serious conditions can cause similar problems and must be ruled out. If you do have Bell’s palsy, early treatment can increase your chances of a full recovery.