Your Nails Could Be Sending Warning Signs — Especially After 40

A line on your nail is not, by itself, a diagnosis.

Different types of nail markings have completely different causes. Some are related to normal aging or minor trauma, while others may provide clues that something affected the body while the nail was growing.

Let’s take a closer look at what these lines can mean—and when they deserve medical attention.

What Are the Lines in the Picture?
The image appears to show transverse markings across the fingernail, with the arrow pointing toward several pale horizontal bands.

Depending on their exact appearance, these could represent different nail changes.

One possibility is a Beau’s line, which is a transverse groove or depression that develops when nail growth is temporarily interrupted.

Another possibility is a type of white nail band known as leukonychia, although the exact appearance and cause matter.

These conditions can look similar in photographs, which is why an image alone cannot reliably identify the cause.

What Are Beau’s Lines?
Beau’s lines are horizontal depressions that extend across the nail.

They occur when nail growth is temporarily slowed or interrupted at the nail matrix—the area beneath the skin at the base of the nail where the nail is produced.

Think of the nail as a timeline.

Something happens to the body → nail growth is temporarily disrupted → the nail continues growing → the previous interruption eventually becomes visible as a horizontal groove.

Because fingernails grow slowly, the position of a line can sometimes provide an approximate clue about when the underlying event occurred.

However, the line itself doesn’t tell you exactly what caused it.

What Can Cause These Nail Grooves?
There are many possibilities.

A temporary interruption in nail growth can occur after:

A significant infection or high fever
Major physical stress
Severe illness
Surgery