Your fingernails can sometimes offer clues about your overall health. While many nail changes are harmless and simply part of aging or minor injuries, certain lines or ridges may occasionally point to underlying medical conditions. Understanding the different types of nail lines can help you know when they're normal—and when it's worth seeking medical advice.
Vertical Ridges
Vertical ridges run from the base of the nail to the tip and are the most common type. They often become more noticeable with age as nail growth changes over time. In most healthy adults, these ridges are considered a normal part of aging and usually don't require treatment.
However, if vertical ridges are accompanied by nail brittleness, discoloration, or changes in nail shape, it may be worth discussing with a healthcare provider, as nutritional deficiencies or certain skin conditions can sometimes contribute.
Horizontal Lines (Beau's Lines)
Horizontal grooves that stretch across the nail are known as Beau's lines. These develop when nail growth temporarily slows or stops due to significant physical stress.
Possible causes include:
- A severe illness with high fever
- Major surgery
- Significant physical trauma
- Poor nutrition
- Certain medications, including some chemotherapy drugs
Because fingernails grow slowly, Beau's lines may appear weeks after the event that caused them.
White Horizontal Lines
White lines across the nails can have different causes depending on their appearance.
- Mees' lines may occur after severe illness, certain medications, or exposure to specific toxins.
- Muehrcke's lines are linked to low blood protein levels and usually do not move as the nail grows.
These findings are uncommon and should be evaluated by a healthcare professional rather than used for self-diagnosis.
Dark Lines
A narrow brown or black line running lengthwise down a nail is called longitudinal melanonychia. In many cases, especially in people with darker skin tones, it is completely harmless.
However, a new dark streak—particularly if it is widening, irregular, affects only one nail, or extends onto the surrounding skin—should be evaluated promptly by a dermatologist. In rare cases, it can be a sign of a serious condition, including melanoma.
Pitted or Grooved Nails
Tiny dents or pits in the nails are commonly associated with skin conditions such as psoriasis and may also occur with eczema or alopecia areata. Deep grooves or other changes in nail texture may also warrant medical evaluation if they persist.
When Should You See a Doctor?
Consider seeking medical advice if you notice:
- A new dark streak on one nail
- Deep horizontal grooves affecting multiple nails
- Nail changes accompanied by pain, swelling, or infection
- Nails becoming thick, brittle, or separating from the nail bed
- Persistent changes that do not improve as the nail grows
