Toenail ridges are almost always caused by normal aging. As you get older, the cells that produce your nail plate slow down and turn over unevenly, creating visible lines that run from the base of the nail to the tip. These vertical ridges are harmless and extremely common. However, ridges that run sideways across the nail, or ridges accompanied by color changes or thickening, can signal something else going on in your body.
Vertical Ridges: Usually Normal
Vertical ridges run lengthwise from your cuticle to the tip of the nail. They’re the most common type of toenail ridge, and in most people they’re simply a sign of aging. The nail matrix (the tissue under your cuticle that generates new nail) gradually changes its turnover rate over the years, producing a surface that’s slightly uneven rather than perfectly smooth. When the ridges are shallow, they’re called onychorrhexis. When they’re deeper, they can look like beading or a string of tiny sausage links running down the nail.
Beyond aging, a few other things can cause or worsen vertical ridges:
- Very dry skin or eczema can produce vertical lines on both fingernails and toenails.
- Iron deficiency has been linked to brittle, ridged nails and, in more severe cases, nails that scoop inward like a spoon.
- Thyroid problems, particularly an underactive thyroid, can make nails thick, brittle, and ridged. You might also notice nails that crumble or break easily.
- Vitamin B12 deficiency can contribute to nail changes including ridging and darkened pigmentation.
If vertical ridges are your only symptom and they’ve developed gradually over months or years, there’s very little reason to worry. They’re the nail equivalent of wrinkles.
Horizontal Ridges: Pay Closer Attention
Horizontal ridges, also called Beau’s lines, are dents or grooves that run sideways across the nail. They form when something temporarily interrupts nail growth. Because toenails grow slowly (roughly 1.5 millimeters per month), a horizontal ridge is essentially a timestamp showing when your body went through a stressful event weeks or months earlier.
Common triggers include:
- Severe illness with high fever, such as COVID-19, pneumonia, or measles
- Injury to the nail, like dropping something heavy on your toe
- Chronic conditions that reduce blood flow to the nail matrix, including diabetes, peripheral artery disease, and Raynaud’s phenomenon
- Skin conditions like psoriasis or eczema
- Zinc deficiency or inadequate protein intake
- Severe emotional stress, such as a major life upheaval or anxiety disorder
- Chemotherapy or prolonged use of artificial nails
A single horizontal ridge on one toenail usually points to a local injury. Horizontal ridges appearing on multiple nails at the same time suggest a systemic cause, meaning something affected your whole body at once.
Ridges vs. Fungal Infections vs. Psoriasis
Not every change in toenail texture is a ridge. Fungal infections are one of the most common toenail problems, and they can look similar at first glance. The key differences: fungal nails tend to turn white, yellow, or brown, look chalky or cloudy in spots, thicken noticeably, and crack or crumble. Ridges alone, without discoloration or significant thickening, are unlikely to be fungal.
Nail psoriasis is another possibility. It causes small pits or dents in the nail surface, sometimes as tiny as a pinpoint and sometimes as wide as a crayon tip. You might have just one or two pits per nail, or more than ten. Psoriasis can also cause the skin under the nail to turn yellow, red, or brown in patches called oil drop spots. If you already have psoriasis on your skin or joints, nail involvement is common. The nails may thin, crumble, or gradually separate from the nail bed.
Nutritional Causes Worth Considering
Several nutrient deficiencies show up in your nails. Iron is the best-studied link: low iron makes nails brittle and ridged, and in more advanced deficiency the nails can become spoon-shaped. Zinc deficiency can trigger horizontal lines and white spots. Low calcium levels may produce ridging alongside white discoloration. Vitamin B12 deficiency often causes nail darkening, but ridging can be part of the picture too.
If you suspect a nutritional cause, a simple blood test can check your levels. Correcting the deficiency typically allows healthier nail to grow in over time, though toenails take six to twelve months to fully replace themselves, so improvement is slow.
What You Can Do About Nail Ridges
For the harmless vertical ridges that come with aging, you won’t eliminate them, but you can improve how your nails look and feel. Keeping nails well-moisturized is the most straightforward approach. Petroleum jelly, urea cream, lactic acid lotion, or mineral oil applied to the nail and surrounding skin all help. For best results, soak your feet in lukewarm water for 10 to 20 minutes first to hydrate the nail plate, then apply moisturizer.
Biotin, a B vitamin found in egg yolks, peanuts, walnuts, and milk, is widely marketed for nail health. The evidence is mixed. Some studies show improvement when biotin is combined with a nail-strengthening lacquer, but on its own the data is limited. It’s unlikely to hurt, since biotin is water-soluble and excess is excreted, but don’t expect dramatic results.
Over-the-counter nail hardeners can temporarily strengthen ridged nails, but they can also paradoxically worsen brittleness over time. The formaldehyde in many formulas is the culprit, and it can cause allergic reactions or nail lifting in some people. If you use one, choose a formaldehyde-free version.
Hydrating nail lacquers containing ingredients like hydroxypropyl chitosan or hyaluronic acid have shown clinically relevant improvements in nail appearance in studies. These coat the nail and help retain moisture without the risks of traditional hardeners.
Signs That Need Medical Attention
Most toenail ridges are cosmetic. But certain nail changes warrant a closer look. A dark brown or black line running vertically down a single nail, especially one that widens over time or extends into the cuticle, can be a sign of subungual melanoma, a type of skin cancer that develops under the nail. These streaks typically start narrower than 3 millimeters and grow. They may look like someone drew a line on the nail with a dark marker.
Other changes worth getting checked: a nail that suddenly changes color, shape, or thickness without any obvious injury; nails that begin lifting away from the nail bed; or horizontal ridges appearing across multiple nails at the same time with no clear cause like a recent illness or fever. These patterns can point to underlying conditions that are treatable once identified.