No one's left and right sides are exactly the same; everyone has some facial asymmetry.
However, when there is a large difference in left–right symmetry—such as a big difference in eyebrow height or one corner of the mouth raised or drooping—
the whole face can look unnatural, as if its center is off.
In more severe cases, the imbalance can spread, resulting in jaw joint problems and posture changes,
and even psychological issues such as social avoidance, so careful care is needed.