A condition that causes sudden, temporary weakness or paralysis of muscles on one side of the face. It occurs due to inflammation of the facial nerve (the seventh cranial nerve), which controls the movement of the facial muscles. The exact cause of Bell’s palsy is unknown, but it is often associated with viral infections, such as the herpes simplex virus (which causes herpes on the lips). Symptoms usually develop quickly and may include sagging face, loss of taste on the affected side, and difficulty closing the eye on that side. Although the condition can be alarming, most people make a full recovery within a few weeks or months, regardless of treatment. In some cases, corticosteroids or physical therapy may be used to relieve symptoms and speed recovery.