Bell's palsy is an unexplained episode of facial muscle weakness or paralysis. It begins suddenly and worsens over 48 hours. This condition results from damage to the facial nerve (the 7th cranial nerve). Pain and discomfort usually occur on one side of the face or head.The cause of Bell's palsy is not known. Bell's palsy is sometimes associated with the diabetes, high blood pressure, Injury, toxins, Lyme disease, Guillain-Barré syndrome, Sarcoidosis,Myasthenia gravis, Multiple sclerosis Infection, especially following a viral infection with Herpes simplex virus (a virus that is related to the cause of the common "cold sores" of the mouth).These are the most common symptoms of Bell's palsy: Disordered movement of the muscles that control facial expressions, such as smiling, squinting, blinking, or closing the eyelid Loss of feeling in the face Headache Tearing Drooling Loss of the sense of taste on the front two-thirds of the tongue Hypersensitivity to sound in the affected ear (hyperacusis) Inability to close the eye on the affected side of the face. There are no specific tests used to diagnose Bell’s palsy. Following test must be done to exclude other disorder: Electromyography (EMG) to determine the extent of the nerve involvement Blood tests to determine if another condition such as diabetes or Lyme disease is present Magnetic resonance imaging (MRI) or computed tomography (CT) to determine if there is a structural cause for your symptoms. Treatment include steroids, antiviral therapy, treat underline cause.