Ridges in your toenails usually fall into one of two categories: vertical lines running from the cuticle to the tip, or horizontal grooves running side to side. Vertical ridges are overwhelmingly common and harmless, especially as you get older. Horizontal ridges are less common and more likely to signal a health issue worth investigating. Understanding which type you have is the first step to knowing whether you need to do anything about it.
Vertical Ridges and Aging
Vertical ridges are the most frequent cause of concern, but they’re rarely a problem. These lines run lengthwise down the nail and tend to become more numerous and noticeable with age. The reason is straightforward: the nail matrix, a small pocket of tissue tucked under your cuticle, is responsible for producing new nail cells. As you age, cell turnover in the matrix slows and becomes less uniform, producing a nail plate with an uneven surface instead of a perfectly smooth one.
Over time, the nail plate itself also becomes more brittle. The once-smooth surface can develop splitting, fissuring, and shallow longitudinal grooves. This is a normal part of aging and doesn’t indicate disease. Nearly everyone develops some degree of vertical ridging by their later decades. If your toenails have only vertical ridges with no color changes, pain, or thickening, there’s generally nothing to treat.
Horizontal Ridges: Beau’s Lines
Horizontal grooves are a different story. Known clinically as Beau’s lines, these are transverse depressions that form when something temporarily interrupts nail growth at the matrix. The nail essentially pauses production for a period, leaving a visible dent that slowly moves forward as the nail grows out.
The list of triggers is broad, but they share a common thread: your body was under significant stress. Beau’s lines have been linked to high fevers, severe infections (including COVID-19), chemotherapy, serious malnutrition, and conditions like Kawasaki disease. Even a single bout of serious illness can produce a groove across one or more nails. Because toenails grow slowly, averaging about 1.6 millimeters per month, a horizontal ridge can take many months to become visible after the triggering event, and even longer to fully grow out.
If you notice horizontal ridges on multiple toenails at the same level, that points to a systemic cause, something that affected your whole body at once. A ridge on just one nail is more likely from localized trauma.
Nutritional Deficiencies
Your nails need a steady supply of nutrients to grow properly, and shortfalls can show up as changes in texture. Iron deficiency is one of the best-documented links. Severe iron deficiency anemia can cause nails to become thin, develop raised ridges, and even curve inward (a spoon-shaped deformity). Zinc deficiency and general protein malnutrition can also disrupt nail growth enough to produce ridging or Beau’s lines.
Biotin, a B vitamin involved in keratin production, is sometimes recommended for brittle or ridged nails. Doses of around 5,000 micrograms daily have been suggested to help strengthen nails, though results vary and it takes months to see any change given how slowly toenails grow. If your diet is reasonably balanced, a deficiency severe enough to cause nail changes is uncommon, but it’s worth considering if you also have fatigue, hair thinning, or other signs of nutritional shortfall.
Trauma and Footwear
Toenails take a beating that fingernails don’t. Ill-fitting shoes, especially ones that are too tight or too short, create repetitive pressure on the nail bed and matrix. Over time, this microtrauma can deform the nail plate, producing ridges, thickening, or splitting. Runners and hikers are particularly prone to this, as the repeated impact of toes hitting the front of the shoe stresses the nail with every step.
A single significant injury to the toe can also cause a ridge if the nail matrix is damaged. The matrix is the only place where new nail tissue is formed, so even a temporary injury there can leave a lasting mark. If the damage is severe enough, the ridge or split may reappear with every new growth cycle. Less severe trauma typically produces a single groove that grows out over the course of 12 to 18 months, given the slow toenail growth rate.
Skin Conditions That Affect Nails
Psoriasis is one of the most common skin diseases to involve the nails. When it affects the nail matrix, it can produce pitting (tiny dot-like depressions), rough ridged surfaces, discoloration, and thickening of the nail bed. You might also notice the nail lifting away from the skin underneath or developing reddish-brown spots that look like oil drops beneath the surface.
Lichen planus, eczema, and a condition called trachyonychia can also roughen the nail surface dramatically. Trachyonychia makes nails look sandpapered, with fine longitudinal ridges covering the entire nail plate. In children, this sometimes appears across all twenty nails at once. These conditions are diagnosed by the pattern of nail changes combined with any skin symptoms elsewhere on the body.
Chronic Health Conditions
Several systemic diseases can alter toenail texture as a secondary effect. Thyroid disorders, both overactive and underactive, commonly cause nails to become brittle, ridged, or prone to separating from the nail bed. Kidney disease can allow waste products to accumulate in the blood, which damages nail growth over time. Heart disease and liver conditions have also been associated with nail changes, though these tend to affect color (pale or white nails) more than texture alone.
When a chronic condition is responsible, the nail changes are rarely the only symptom. You’ll typically notice other signs, fatigue, swelling, weight changes, skin dryness, that point to the underlying problem. Treating the root condition often improves nail appearance, though it takes a full growth cycle (roughly 12 to 18 months for a toenail) before you see the results.
Keeping Ridged Nails Healthy
For vertical ridges, the goal is maintenance rather than cure. Keeping nails moisturized with a simple emollient or cuticle oil helps reduce brittleness and the splitting that makes ridges more visible. Avoiding prolonged water immersion and harsh chemicals (like acetone-based removers) also protects the nail plate. Some people find that a clear nail polish with added protein gives the nail a smoother appearance and an extra layer of protection.
Wearing properly fitted shoes is one of the most effective things you can do for your toenails. There should be about a thumb’s width of space between your longest toe and the end of the shoe. This is especially important during exercise, when feet swell and shift forward with each stride.
Warning Signs Worth Checking
Most toenail ridges are harmless, but certain changes alongside ridging warrant attention. Be alert to nails that change color, especially dark streaks or bands running lengthwise, which can occasionally indicate subungual melanoma (a type of skin cancer under the nail). Nails that suddenly change shape, begin lifting from the nail bed, develop an ulcer or nodule, or start bleeding without clear injury should be evaluated. Darkening of the skin around the nail, known as the Hutchinson sign, is a particularly important red flag. These changes are uncommon, but catching them early makes a significant difference in outcomes.