Bell's palsy
The symptoms of Bell’s palsy include sudden weakness in your facial muscles. In most cases, the weakness is temporary and significantly improves over weeks. The weakness 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 acute peripheral facial palsy of unknown cause, can occur at any age. The exact cause is unknown. It’s believed to be the result of swelling and inflammation of the nerve that controls the muscles on one side of your face. Or it might 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. 
Symptoms
Signs and symptoms of Bell’s palsy come on suddenly and may include:- Rapid onset of mild weakness to total paralysis on one side of your face — occurring within hours to days
- Facial droop and difficulty making facial expressions, such as closing your eye or smiling
- Drooling
- Pain around the jaw or in or behind your ear on the affected side
- Increased sensitivity to sound on the affected side
- Headache
- A loss of taste
- Changes in the amount of tears and saliva you produce