Bell's palsy is a peripheral palsy of the facial nerve that results in muscle weakness on one side of the face. Affected patients develop unilateral facial paralysis over one to three days with forehead involvement and no other neurologic abnormalities. Symptoms typically peak in the first week and then gradually resolve over three weeks to three months. Bell's palsy is more common in patients with diabetes, and although it can affect persons of any age, incidence peaks in the 40s. Bell's palsy has been traditionally defined as idiopathic; however, one possible etiology is infection with herpes simplex virus type 1. Laboratory evaluation, when indicated by history or risk factors, may include testing for diabetes mellitus and Lyme disease. A common short-term complication of Bell's palsy is incomplete eyelid closure with resultant dry eye. A less common long-term complication is permanent facial weakness with muscle contractures. Approximately 70 to 80 percent of patients will recover spontaneously; however, treatment with a seven-day course of acyclovir or valacyclovir and a tapering course of prednisone, initiated within three days of the onset of symptoms, is recommended to reduce the time to full recovery and increase the likelihood of complete recuperation.