Bell’s palsy is a condition that causes muscle weakness or paralysis in the facial muscles. When a person has Bell’s palsy, it looks like their face is drooping on one side. It is possible for Bell’s palsy to affect both sides of the face, however this is rarely seen. Bell’s palsy is also known as facial palsy. It is unclear what causes Bell’s palsy, however some believe that it is caused by inflammation and swelling that occurs in the nerve that controls the muscles on the side of the face that it affects.