Toenail ridges are usually caused by normal aging. As you get older, the rate at which nail cells turn over slows and becomes less uniform, producing visible lines that run from the cuticle to the tip of the nail. These vertical ridges are the most common type, and in most cases they’re completely harmless. Horizontal ridges, on the other hand, can signal that something disrupted your nail growth, and they’re worth paying closer attention to.
Vertical Ridges vs. Horizontal Ridges
The direction of the ridges on your toenails tells you a lot about what’s causing them. Vertical ridges run lengthwise, from the base of the nail to the free edge. They tend to become more numerous and prominent with age, and they’re a normal part of how nails change over time. Almost everyone develops some degree of vertical ridging eventually.
Horizontal ridges run side to side across the nail. Dermatologists call these Beau’s lines, and they form when something temporarily slows or stops nail growth. As the nail resumes growing, a groove or dent marks the spot where growth paused. If you see deep horizontal grooves on one or more toenails and can’t think of an obvious cause like stubbing your toe, it’s worth getting them evaluated.
Common Causes of Vertical Ridges
Age is the leading cause, but it’s not the only one. Several nutritional shortfalls can make vertical ridges worse or cause nails to become brittle alongside the ridging. Iron deficiency is a well-documented trigger, producing both ridging and nails that crack or split easily. Zinc deficiency can do the same. Low calcium levels have also been linked to longitudinal ridging and brittle nails.
Dehydration of the nail plate plays a role too. Toenails that are repeatedly exposed to moisture and then allowed to dry out (from showering, swimming, or sweating in shoes) lose flexibility and develop more visible texture over time. People who spend long hours in closed-toe shoes without moisture-wicking socks often notice more prominent ridges.
In rare cases, a condition called trachyonychia causes extreme ridging across multiple nails. The nails take on a rough, sandpaper-like texture with prominent longitudinal ridges and frequent splitting. Trachyonychia can appear on its own or alongside autoimmune conditions like alopecia areata.
What Horizontal Ridges Can Mean
Because horizontal ridges reflect a disruption in nail growth, the list of possible causes is broad. Acute illnesses are a common trigger. High fevers, pneumonia, severe infections, and even COVID-19 can all produce Beau’s lines weeks after the illness has passed. The groove appears at the base of the nail once growth resumes, then gradually moves toward the tip as the nail grows out. Since toenails grow slowly (roughly 1.5 millimeters per month), you might not notice the line until months after you were sick.
Chronic conditions that reduce blood flow to the nail matrix are another cause. Diabetes, hypothyroidism, peripheral artery disease, and Raynaud’s phenomenon can all interfere with the steady nutrient supply your nails need to grow smoothly. Skin conditions like psoriasis and eczema can affect the nail bed directly, producing ridges, pitting, or thickening.
Physical trauma is a straightforward trigger. Dropping something on your toe, wearing shoes that press hard against the nail, or exposing your feet to extreme cold can all damage the nail matrix enough to leave a horizontal groove. Severe zinc deficiency, inadequate protein intake, and even intense emotional stress (grief, anxiety disorders, major life upheaval) have been linked to Beau’s lines as well.
Fungal Infections and Psoriasis
Two conditions that commonly affect toenails can look deceptively similar at first glance, but they produce different patterns. Knowing the difference helps you describe what you’re seeing if you visit a doctor.
Nail fungus typically starts in a single toenail. You’ll notice yellow or white streaks, thickening of the nail, and brittleness. The nail may crumble at the edges. If you also have athlete’s foot (itchy, peeling skin between the toes), a fungal nail infection is the most likely explanation. Fungus doesn’t usually cause the small, uniform pits that psoriasis does.
Nail psoriasis tends to affect multiple nails and produces tiny divots on the nail surface that look like someone pressed a tack into the nail. You may also see reddish-brown splotches underneath the nail (sometimes called oil spots) and a pinkish line where the nail lifts away from the bed. In nearly every case of nail psoriasis, there are signs of psoriasis somewhere else on the body, since it’s a systemic inflammatory disease.
Nutritional Fixes That Help
If your ridges are related to a nutritional gap, correcting the deficiency can improve nail texture over time. The challenge is that toenails grow slowly, so visible improvement takes months. Biotin is the most studied supplement for brittle, ridged nails. Clinical trials show benefits typically start after two to three months of daily supplementation. Iron supplementation has been shown to reduce nail brittleness even in people without a diagnosed iron deficiency. Silicon supplements may also improve the appearance of weak, ridged nails.
Before supplementing, it’s worth checking whether a deficiency actually exists. A simple blood panel can measure iron, zinc, and other nutrient levels. Taking high-dose iron or zinc without a deficiency can cause side effects and won’t necessarily help your nails.
Daily Care to Minimize Ridges
You can’t stop age-related ridging entirely, but keeping the nail and surrounding skin well-moisturized makes a noticeable difference in how prominent the ridges look and how often nails crack along them. Apply a cuticle oil or thick foot cream daily, focusing on the base of each toenail where new growth forms. Ingredients like vitamin E, jojoba oil, and shea butter are particularly effective at maintaining moisture in the nail plate.
A few other habits help. Keep your toenails trimmed straight across to reduce stress on the nail. Avoid picking at or pushing back cuticles aggressively, since the cuticle protects the nail matrix underneath. If you wear nail polish, give your nails regular breaks. Nail-strengthening treatments containing keratin, biotin, or calcium, applied once or twice a week, can reinforce nails that are prone to splitting along ridges.
Signs That Need Professional Attention
Most toenail ridges don’t require medical care, but certain changes alongside ridging are red flags. A new or changing dark streak under the nail needs prompt evaluation, as it can be a sign of melanoma. Nails that turn yellow, thicken, and seem to stop growing can indicate lung disease, rheumatoid arthritis, or serious infection. Greenish-black discoloration points to a bacterial infection that will worsen without treatment.
Nails that curve dramatically downward (clubbing) can reflect problems in the lungs, heart, or liver. Spoon-shaped nails that dip in the center suggest iron deficiency. And if a nail lifts away from the bed, showing white discoloration underneath, a dermatologist or podiatrist should take a look regardless of whether ridges are present. These changes aren’t about cosmetics. They’re your body flagging something internal through one of the few tissues you can see every day.