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Bell's palsy is a paralysis or weakness of the muscles on one side of your face. Damage to the facial nerve that controls muscles on one side of the face causes that side of your face to droop. The nerve damage may also affect your sense of taste and how you make tears and saliva. This condition comes on suddenly, often overnight, and usually gets better on its own within a few weeks.
Bell's palsy is not the result of a stroke or a transient ischemic attack (TIA). While stroke and TIA can cause facial paralysis, there is no link between Bell's palsy and either of these conditions. But sudden weakness that occurs on one side of your face should be checked by a doctor right away to rule out these more serious causes.