Though aging and illness are responsible for the vast majority of nail ridges, they are not the only sources. Injuries, even if they do not show damage at the time, can cause the nails to grow incorrectly. The nail does not stop at the cuticle. Instead, it continues into the finger for a short distance. Scratches, blunt traumas, and other accidents to this hidden section of the nail can cause scrapes and ridges. Once the nail grows, and the previously hidden damage is exposed, it may seem as though a new ridge has developed. Given the time it takes nails to grow, one may forget the injury by the time the damage appears.

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