Vertical Lines

Vertical lines are ridges that extend from the cuticle to the tip of the nail. Generally, older adults tend to develop slight vertical ridges due to a decrease in cell renewal. This occurs when new cells wait beneath the skin’s surface to replace the dead cells on the outside.

If other abnormalities are also present, such as changes in color and texture, an underlying condition may be suspected. For example, in trachyonychia, a condition that can be an isolated phenomenon or linked to other skin disorders, the nail ridges change color, and their surface becomes rough and brittle.

Similarly, people with iron deficiency anemia may also present with vertical lines. Likewise, changes in shape can give the nails a concave or spoon-like appearance.

Horizontal Lines

Horizontal ridges, also known as Beau’s lines, are considered a symptom of more serious diseases. These indentations on the nail surface can impede nail growth until the underlying condition is detected and treated.

Beau’s lines are an indication of acute kidney disease, and when they develop on all 20 nails, they suggest the presence of mumps, thyroid disease, diabetes, or syphilis. According to a study published in Acta Haematologica, they also appear in patients undergoing chemotherapy.

A blow or trauma is another reason why red or brown spots develop under the nails. It’s important to be very careful not to confuse these changes in color with symptoms of diseases such as endocarditis or melanoma. In those cases, you should be alert for a dark brown, black, or red color.