If you’re referring to
lines or ridges on the fingernails, most are harmless, but some patterns deserve attention.
- Vertical ridges (from cuticle to tip) are very common and often become more noticeable with age.
- Horizontal grooves/lines (across the nail), called Beau’s lines, can occur when nail growth is temporarily interrupted—for example, after significant illness, injury, or severe stress.
- A dark brown/black line under one nail can have several causes, including trauma or pigmentation. A new or changing dark streak should be assessed by a clinician because, rarely, it can be a sign of nail melanoma.
- White lines or spots are usually caused by minor nail injury, although widespread or unusual changes can sometimes have other causes.
The important point is that nail lines alone usually can’t diagnose a vitamin deficiency or other disease. If a line is new, appears on only one nail, is getting wider/darker, or the surrounding skin is also becoming pigmented, it’s worth getting it checked.
