If you have Bell's palsy, the muscles in your face become temporarily paralyzed. It usually affects just one side of the face. Symptoms appear suddenly - you can't shut your eye and your mouth droops. Symptoms are usually worst about 48 hours after they start. Scientists think that a viral infection makes the facial nerve swell or become inflamed. You are most likely to get Bell's palsy if you are pregnant, diabetic or sick with a cold or flu. Three in four patients improve without treatment. With or without treatment, most people begin to get better within 2 weeks and most recover completely within 3 to 6 months.