Ridges on your nails are almost always harmless, especially if they run vertically from the base of the nail to the tip. These vertical lines are one of the most common nail changes and become more noticeable with age. Horizontal ridges, on the other hand, can signal that something temporarily disrupted your nail growth and are worth paying closer attention to.
The direction of the ridges matters. Understanding whether yours run up-and-down or side-to-side tells you a lot about what’s going on.
Vertical Ridges Are Usually Normal
Vertical ridges run from your cuticle to the tip of your nail, like tiny lines etched into the surface. They’re extremely common and, in most cases, are simply a sign of aging. As you get older, your nails naturally lose moisture and the nail plate becomes slightly uneven in thickness, creating those visible lines. Think of them as the nail equivalent of fine wrinkles.
Beyond aging, a few other things can cause or worsen vertical ridges:
- Dry skin or eczema. If your skin tends to be dry or you have eczema, your nails may show more pronounced vertical lines.
- Thyroid problems. An underactive thyroid can produce thick, brittle nails with visible ridges. You’d typically notice other symptoms too, like fatigue, weight gain, or feeling cold all the time.
- Iron deficiency. Low iron levels can cause vertical ridges along with a distinctive change where the nails curve inward like a spoon, a condition called koilonychia. If your nails look scooped out in the center, that’s a reason to get your iron levels checked.
If you only notice mild vertical lines and your nails otherwise look healthy, there’s generally nothing to worry about. They’re cosmetic, not medical.
Horizontal Ridges Signal Disrupted Growth
Horizontal ridges are different. These run side to side across the nail and are called Beau’s lines. They form when something interrupts nail growth temporarily, creating a visible dent or groove as the nail grows out. Your nails grow from the matrix, a small area tucked under the cuticle. When the body is under significant stress, the matrix briefly pauses or slows production, leaving a mark in the nail plate.
Common triggers include:
- Severe illness with high fever, such as COVID-19, pneumonia, or measles
- Chemotherapy
- Direct injury to the nail, like slamming your finger in a door
- Long-term use of acrylic or gel nails, which can damage the nail bed over time
- Poor circulation from peripheral vascular disease
- Nutritional gaps, particularly severe zinc deficiency or inadequate protein intake
Zinc deficiency can also cause white spots on the nails alongside those horizontal grooves.
Using Ridges as a Timeline
Here’s something useful: because fingernails grow at an average rate of about 3.5 millimeters per month, you can estimate when the disruption happened by measuring how far the ridge is from your cuticle. A Beau’s line sitting about 7 millimeters from the base of your nail likely formed around two months ago. If you had a bad flu or a hospital stay around that time, that’s your answer. Toenails grow much slower, roughly 1.6 millimeters per month, so horizontal ridges on toes take longer to appear and longer to grow out.
Nail Psoriasis Looks Different
Psoriasis can affect nails in ways that sometimes get confused with ordinary ridges. Nail psoriasis typically causes small pits or dents in the nail surface, ranging from pinpoint-sized to about 2 millimeters across. Some people develop just one or two pits, while others have more than ten per nail. Psoriasis can also produce horizontal grooves similar to Beau’s lines.
The key difference is that psoriasis pits tend to be scattered and irregular rather than forming a clean line across the nail. If you already have psoriasis on your skin or scalp, nail changes are common. Up to half of people with skin psoriasis eventually notice it in their nails too.
Why You Shouldn’t Buff Ridges Away
It’s tempting to grab a nail buffer and smooth out those vertical lines, but this actually makes things worse. The grooves between ridges are already 5 to 7 percent thinner than the surrounding nail. When you buff down the raised portions to match, you’re thinning the entire nail plate to its weakest point. Those thinned-out areas are more prone to cracking, and once a crack starts, the nail layers begin peeling apart, leading to splitting and breakage that’s hard to recover from.
A better approach is using a ridge-filling base coat. These products fill in the grooves without removing any nail material, creating a smooth surface. They also help prevent staining from colored nail polish and give polish a better surface to adhere to. If your ridges bother you cosmetically, this is the safer route.
For ridges caused by dryness, regularly moisturizing your nails and cuticles with a thick cream or cuticle oil can reduce their appearance over time. If an underactive thyroid or iron deficiency is the underlying cause, treating that condition often improves nail texture as new nail grows in.
Signs That Need Medical Attention
Most ridges are benign, but certain nail changes warrant a closer look. A dark streak running lengthwise through the nail, particularly one with irregular pigment that isn’t evenly colored, can be a sign of a type of melanoma that develops under the nail. This is rare, but it’s something to take seriously.
Other changes worth bringing up with a doctor include nails that suddenly change shape or thickness, nails lifting away from the nail bed, swelling or inflammation around the nail, or discoloration of the skin surrounding the nail (sometimes called Hutchinson sign). Bleeding, ulcers, or nodules near the nail also fall into this category.
Horizontal ridges appearing on multiple nails at the same time, without an obvious explanation like a recent illness, are also worth investigating. They can point to an undiagnosed nutritional deficiency or circulatory issue that a simple blood test can identify.