Bell's palsy causes sudden weakness in your facial muscles. This makes half of your face appear to droop. Your smile is one-sided, and your eye on that side resists closing.
Bell's palsy, also known as facial palsy, can occur at any age. The exact cause is unknown, but it's believed to be the result of swelling and inflammation of the nerve that controls the muscles on one side of your face. It may be a reaction that occurs after a viral infection.
For most people, Bell's palsy is temporary. Symptoms usually start to improve within a few weeks, with complete recovery in about six months. A small number of people continue to have some Bell's palsy symptoms for life. Rarely, Bell's palsy can recur.