Bell's palsy occurs when the nerve that controls facial muscles on one side of your face (the 7th cranial nerve) swells or becomes inflamed. It can affect anyone, but mostly occurs in people between the ages of 15 and 60 years old.
Most people who have Bell's palsy find their symptoms improve within a few weeks and they recover completely in three to six months. Approximately 10 percent of people who have Bell's palsy once will get it again, either on the same side or the other side of the face.
This condition rarely affects both sides of the face, however, it can happen. If this bilateral form of Bell's palsy occurs, or if any other part of the body becomes paralyzed, weak or numb, it is important for your doctor to rule out other causes.