Bell's palsy causes sudden and temporary weakness in the facial muscles. This makes half of the face look droopy. The smile is drawn from only one side and one of the eyes does not close completely.

Bell's palsy or facial paralysis can happen at any age. The cause is not known exactly. It is believed to be the result of swelling and inflammation of the nerve that controls the muscles on one side of the face. It can also be a reaction after a viral infection.

In most cases, Bell's palsy is temporary. Usually, the symptoms begin to improve within a few weeks and full recovery is achieved in about six months. There are a small number of people who continue to have Bell's palsy symptoms for life. It is rare for Bell's palsy to come back.