What causes bell's palsy?

The facial nerve carries signals to muscles that close the eye, raise the eyebrow and move the mouth. When the nerve becomes inflamed inside the narrow space through the skull, those signals are interrupted. Weakness can develop over hours and affect one side of the face, with a drooping mouth, difficulty closing the eye, altered taste or sensitivity to sound. The precise cause is often uncertain. Reactivation of a virus that remains inactive in the body is one possible explanation; shingles can also affect nerves and produce facial weakness, sometimes with a painful rash or blisters.

Arrange urgent medical assessment for new one-sided facial weakness because Bell's palsy resembles other conditions that need different treatment. A clinician may prescribe treatment early in the course when appropriate. Protect an eye that does not close fully with the recommended lubricating drops, ointment or covering, and avoid letting it dry or become injured. Do not use leftover medicines without advice. Note when symptoms began and whether there is pain, a rash, limb weakness or speech change.

Call emergency services immediately if facial drooping starts suddenly with arm or leg weakness, speech difficulty, confusion, severe headache, loss of balance or trouble swallowing. These signs may indicate a stroke. Urgent assessment is also needed for severe ear pain, blisters around the ear or eye, or an eye that cannot be protected.

Ask whether the pattern fits Bell's palsy, how to protect the affected eye, whether treatment is time-sensitive, what symptoms suggest shingles or stroke, and when facial movement should be reviewed.