Lines on nails are common and often harmless. Nails grow from the matrix beneath the cuticle, and as they form, they reflect what’s happening in the body. Because nails grow slowly, they can act like a timeline of health, stress, and aging.

Vertical ridges are the most common type. They run from the base to the tip and are usually a normal part of aging, caused by slower and less uniform cell production over time. In most cases, these ridges don’t signal disease. However, if they become more noticeable or appear alongside changes in color, thickness, or brittleness, they may point to nutritional deficiencies such as low iron, zinc, protein, or certain vitamins, or to skin conditions like eczema that disrupt normal growth patterns.

Horizontal lines, known as Beau’s lines, are less common and may indicate a temporary interruption in nail growth due to stress, illness, or fever. These lines form when the body redirects energy away from nail production during difficult periods. As the nail grows, the line moves outward, marking exactly when the disruption occurred.

Not all nail changes come from internal issues. Injuries, chemicals, moisture, or cosmetic treatments like acrylics can also cause ridges or discoloration. Overall, nail changes should be viewed in context. Gradual, stable ridges are usually harmless, while sudden or widespread changes may be worth checking with a professional.