Why do Beau's lines cause ridged nails?

The nail plate is made at its root, beneath the skin fold at the base of the nail. If growth slows or stops for a time, less nail material is produced. When growth resumes, the newer nail continues forward, leaving a horizontal groove or depression across the plate. This mark is called a Beau's line.

The line moves toward the fingertip as the nail grows. Its position can give a clinician an approximate sense of when the interruption occurred, but it does not identify one specific cause. Fever, significant illness, injury to the nail root, severe stress on the body, or some treatments can interrupt growth. Several nails affected together may suggest a body-wide event, while one nail may point to local trauma.

Let the nail grow out without picking at the groove. Keep nails trimmed, protect them from repeated pressure, and use gloves for wet or chemical work. Note whether one or several nails are affected and whether the change began after an illness, injury, or treatment. A clinician can examine the nail root and surrounding skin if the cause is unclear.

Arrange an assessment if grooves recur, involve many nails, or appear with nail lifting, marked colour change, swelling, drainage, or pain. Seek earlier care after significant injury to the nail root or when you feel generally unwell.

Does the pattern fit a past interruption in nail growth? Could the groove be related to trauma, infection, or a medicine? Should I monitor other nails or have the nail root examined?