Beau's lines are grooved lines that run in which direction across the nail bed?

• A. Across the nail length
• B. Side-to-side, horizontally across the nail bed
• C. Diagonally from root to tip
• D. Circular around the nail

Answer: (B)

Beau's lines are transverse grooves that run side-to-side across the nail plate. They form when nail matrix production temporarily pauses due to illness, injury, or systemic stress. As the nail grows outward from the proximal root, that pause shows up as a horizontal line stretching from one edge of the nail to the other. This direction is perpendicular to the nail’s growth, so the lines cross the nail rather than run along its length. If a line ran lengthwise, diagonally, or circularly around the nail, it wouldn’t match Beau's lines.