Nails that curl inward and downward, wrapping around the fingertip or toe, are usually exhibiting a condition called pincer nail deformity. This happens when the nail plate develops excessive transverse curvature that increases from the base toward the free edge, sometimes pinching the underlying skin hard enough to cause real pain. The causes range from something as simple as tight shoes to underlying health conditions like fungal infections or psoriasis, and the good news is that most cases respond well to treatment once you identify what is driving the curling.
How Nails Normally Stay Flat
Your nail plate has a natural tendency to curve. Under normal conditions, this inward-curving force is kept in check by upward mechanical pressure from the fingertip or toe pad pushing back against the nail from below. Researchers have described this as an “automatic curvature function,” where the nail’s built-in desire to roll inward is balanced by the ground reaction forces you generate just by walking, gripping, and using your hands. When that balance tips in favor of the curving force, the nail starts rolling under. When the upward force wins instead, you can get the opposite problem: nails that scoop outward like a spoon.1PubMed Central. Clinical Evidence for the Relationship between Nail Configuration and Mechanical Forces
This balance model helps explain why curling is far more common on toenails than fingernails. Toes are squeezed into shoes, pressed against hard surfaces, and subjected to repetitive impact forces. Anything that disrupts either side of the equation, whether it reduces the upward push (like being bedridden and not walking) or increases the inward pull (like a genetic predisposition to excessive curvature), can tip the nail into a curling pattern.
The Most Common Causes of Inward Curling
Tight or Ill-Fitting Footwear
Shoes that compress the toes, especially pointed-toe styles and high heels, are one of the most frequently cited triggers for pincer nails. The external pressure pushes the nail edges downward over time, encouraging the plate to curl rather than grow flat. Pincer nail deformity has been directly attributed to tight footwear alongside factors like gait abnormalities and anatomical variations in how the nail sits on the toe.2PubMed Central. An Uncommon Cause of Pincer Nail If you have recently changed shoe styles or started wearing a pair that pinches across the toe box, that alone could be enough to set the process in motion.
Genetic and Inherited Tendencies
Some people are simply born with nail plates that curve more aggressively. A genetic predisposition can increase the automatic curvature force beyond what normal daily activity can counterbalance.1PubMed Central. Clinical Evidence for the Relationship between Nail Configuration and Mechanical Forces Pincer nails sometimes run in families, showing up on multiple toes and sometimes on fingers as well. In congenital cases, the curling tends to be symmetrical, affecting the same nails on both feet, and it often becomes more pronounced with age even without any obvious external trigger. A comprehensive review of pincer nail deformity identifies hereditary factors as one of several established causes, alongside acquired ones like trauma and systemic disease.3PubMed Central. Pincer Nail Deformity: Clinical Characteristics, Causes, and Managements
Fungal Nail Infections
Onychomycosis, the medical term for a fungal nail infection, is one of the more overlooked reasons nails start curling. The fungus invades the nail plate and bed, gradually thickening and distorting the nail. As the infected nail grows denser and more brittle, it loses its normal flexibility and begins to warp, often curving downward or developing an irregular shape. Fungal infections are notoriously stubborn because antifungal drugs have trouble penetrating the thick nail plate, and recurrence rates are high even after apparently successful treatment.4PubMed Central. Transfersome enhances nail penetration of antifungal drug and photosensitizer for chemo-photodynamic therapy of onychomycosis in a novel rat model If your curling nail is also yellowish, crumbly, or unusually thick, a fungal infection is worth investigating.
Psoriasis and Psoriatic Arthritis
Nail changes are remarkably common in people with psoriasis. Roughly half of people with skin psoriasis and up to 80% of those with psoriatic arthritis develop nail problems, including thickening, loosening of the nail from its bed, and changes in nail shape that can include inward curling.5PubMed Central. Nail involvement in psoriatic arthritis Psoriatic nail disease affects the matrix (where the nail is made) and the bed (what the nail sits on), so the distortion comes from the inside out. If you have psoriasis plaques elsewhere on your skin, or if you have joint stiffness along with nail changes, the curling could be part of a broader inflammatory picture rather than a standalone nail problem.
Bony Growths Under the Nail
Sometimes the nail curls because something underneath it is physically pushing it out of shape. Subungual exostosis, a benign bony growth on the tip of the toe bone, can press upward against the nail bed and distort the nail plate. This has been documented in patients of various ages, from children to adults in their late thirties, and it typically affects the big toe.6PubMed Central. Dystrophy of the Great Toenail by Subungual Exostosis and Hyperostosis: Three Case Reports with Different Clinical Presentations The nail dystrophy in these cases can look like a pincer nail or an ingrown nail, but the underlying cause is skeletal rather than a problem with the nail itself. An X-ray is usually enough to spot the growth.
Why Nails Curl More as You Age
If your nails have gradually started curling in your fifties, sixties, or beyond, age itself may be part of the explanation. Nail growth slows with age, circulation to the extremities decreases, and the nail plate tends to thicken and become more brittle. These changes can affect every part of the nail unit, and they sometimes represent normal aging rather than disease.7PubMed Central. Common nail changes and disorders in older people: Diagnosis and management That said, dismissing curling nails as “just getting old” can mean missing a treatable cause. Fungal infections, for instance, become more common with age and can make age-related thickening worse. A doctor can help sort out which changes are part of normal aging and which ones need attention.
Reduced mobility also plays a role. People who walk less, whether because of arthritis, recovery from surgery, or simply a more sedentary lifestyle, lose some of the upward mechanical force that keeps nails flat. This is the same mechanism that causes curling in bedridden patients: without the ground pushing back against the nail, the natural curvature goes unchecked.
When Curling Nails Become a Real Problem
Mild curling on its own is mostly cosmetic. But pincer nail deformity in its more advanced form can cause significant pain. The edges of the curled nail dig into the soft tissue of the nail fold, sometimes creating an ingrown nail that gets infected. Researchers who study pincer nails consistently describe the condition as one that can cause intractable pain and meaningfully decrease quality of life.8PubMed. A simple therapeutic approach to pincer nail deformity using a memory alloy: measurement of response Walking becomes uncomfortable, closed shoes feel unbearable, and the appearance of the nail bothers many people enough to avoid sandals or going barefoot.
Infection is the main medical risk. When the nail edge breaks the skin, bacteria can enter and cause redness, swelling, and pus. For people with diabetes or compromised circulation, even a minor nail-fold infection can spiral into a serious wound-care issue. If you notice warmth, redness, or drainage around a curling nail, that warrants prompt medical attention rather than a wait-and-see approach.
Conservative Treatments That Avoid Surgery
For many people, the curling can be corrected without going under the knife. The first and simplest step is addressing external causes: switching to wider, lower-heeled shoes, keeping nails trimmed straight across rather than curved, and treating any underlying fungal infection.
Nail bracing is one of the most effective non-surgical options. A small clip or wire is attached to the nail plate, applying gentle outward tension that gradually flattens the curve over weeks to months. The approach is safe, inexpensive, requires no anesthesia, causes no recovery downtime, and provides immediate relief from the pressure pain that pincer nails cause.9PubMed Central. Ingrown toenails (unguis incarnatus): Nail braces/bracing treatment You can wear your regular shoes and go about your day while the brace does its work. Several types exist, including spring-wire braces and flat composite strips, and a podiatrist or dermatologist can fit them in an office visit.
A newer conservative approach, sometimes called orthonyxia, uses custom-shaped corrective devices applied directly to the nail. A pilot study in diabetic patients, a population that particularly benefits from avoiding surgery, found that this type of conservative treatment outperformed traditional nail reconstruction methods. Patients in the corrective-device group had far lower recurrence rates (about 15% compared to 75% with the older method) and significantly more pain-free days over the follow-up period.10Journal of Advanced Health Care. Ingrown toenails treatment in diabetic patients: a Pilot Study of a new conservative treatment of orthonyxia That is a striking difference, though the study was small and results may vary in broader populations.
When Surgery Makes Sense
If bracing fails, the deformity is severe, or the nail keeps growing back curled after conservative treatment, surgery becomes the next step. Several techniques exist, and the choice depends partly on the anatomy of your specific nail and partly on the blood flow to your foot.
One well-studied approach involves detaching the nail plate, correcting the overcurvature, and then reconstructing the nail bed so the nail grows back flatter. Surgeons who developed one such technique reported that it was relatively quick and straightforward, with lower rates of complications like skin death or infection compared to some older surgical methods.11PubMed Central. Nail Plate and Bed Reconstruction for Pincer Nail Deformity Another study compared two different surgical methods, a zigzag flap and an inverted-T incision, and chose between them based on the circulatory condition of the patient’s foot. Both produced satisfactory results, but the authors emphasized that assessing blood flow before deciding on a technique matters for healing.12PubMed Central. Anatomical characteristics and surgical treatments of pincer nail deformity
In some cases, a combination approach is used: the nail matrix is partially destroyed with a chemical (usually phenol) to narrow the nail permanently, combined with an incision down the center of the nail and splinting to hold the corrected shape while it heals.13PubMed. Combined surgical treatment of a pincer nail with chemical matricectomy, median nail incision, and splinting Partial matricectomy means the nail that grows back is narrower, which reduces the surface area available for curling. The trade-off is a permanently thinner nail, but for someone who has been in chronic pain, that is usually a welcome exchange.
Fingernails Versus Toenails
Most of the clinical literature on curling nails focuses on toes, especially the big toe, because that is where the problem is most common and most painful. But fingernails can curl under too, and the causes overlap only partially. Fingernails are less subject to compression from footwear and repetitive ground impact, so when they curl, the explanation is more likely to be systemic: a nutritional deficiency, a skin condition like psoriasis, a fungal infection, or a hereditary tendency. Iron deficiency is one of the better-known nutritional causes of nail shape changes, though severe iron deficiency more classically produces spoon-shaped nails (the opposite direction of curling) rather than pincer nails. If your fingernails specifically are curling inward, it is worth mentioning to your doctor because the differential diagnosis is a bit different from what it would be for a toenail.
Repetitive trauma to fingernails can also cause curling. People who use their nails as tools, prying things open, scraping surfaces, or typing on hard keyboards for hours, subject the nail plate to forces that can distort it over time. Musicians who play stringed instruments sometimes develop nail changes on their fretting hand. The solution in these occupational cases is often practical: adjust how you use your hands, keep nails short, and let damaged nails grow out.
Nutritional Deficiencies and Nail Shape
You will find plenty of claims online that curling nails signal a vitamin deficiency, and there is some truth to this, but it is less straightforward than the internet makes it sound. Iron, biotin, zinc, and B12 have all been linked to nail abnormalities in various studies, but the nail changes associated with deficiencies are usually more generalized: brittleness, ridging, thinning, or discoloration rather than the specific transverse curling of a pincer nail. Severe iron deficiency can reshape nails, but as noted above, it tends to push them in the opposite direction.
Biotin supplementation has become popular for nail health, and there is limited evidence it can improve brittle nails in people who were genuinely deficient. But biotin deficiency is uncommon in people eating a reasonably varied diet, and taking extra biotin when you are not deficient has not been shown to change nail shape. If you suspect a nutritional cause, the more productive step is getting bloodwork done rather than loading up on supplements. A doctor can check iron, ferritin, B12, and zinc levels quickly, and targeted treatment of an actual deficiency is more effective than guessing.
Memory Alloy Clips and Newer Devices
One of the more interesting developments in non-surgical correction involves shape-memory alloy clips. These small metal devices are made from alloys that “remember” a flat shape: you bend them to fit the curved nail, and as body heat warms the metal, it gradually returns to its original flat configuration, pulling the nail edges outward with it. Researchers have used these clips as a simple therapeutic approach and measured the resulting changes in nail curvature, finding that they produced meaningful correction.8PubMed. A simple therapeutic approach to pincer nail deformity using a memory alloy: measurement of response The appeal is that they are discreet enough to wear under shoes, do not require anesthesia, and can be adjusted or replaced as the nail grows.
These devices are not yet widely available everywhere. Availability depends on where you live and whether your podiatrist or dermatologist stocks them. But they represent a growing trend toward corrective devices that work passively over time rather than requiring a single corrective event. If bracing interests you, ask your provider specifically about shape-memory alloy options in addition to traditional wire or composite braces.
What to Do Right Now If Your Nails Are Curling
Start with the low-hanging fruit. Look at your shoes: are they compressing your toes? Look at your nails: are they discolored, thickened, or crumbly in a way that suggests fungus? Think about timing: did the curling start after a medication change, an illness, or a period of immobility? Any of these observations gives your doctor a head start on figuring out the cause.
For immediate comfort, soaking the affected nail in warm water for 10 to 15 minutes softens the plate and relieves some of the pressure on the nail folds. If the edges are digging into skin, gently lifting the nail corner and placing a small piece of cotton or dental floss underneath can provide temporary relief. Do not try to cut or dig out an ingrown portion yourself, especially on a toenail, because you risk introducing infection.
See a doctor or podiatrist if the curling is painful, if there are signs of infection, if the nail is severely deformed, or if simple measures have not helped after a few weeks. A professional can trim the nail properly, fit a brace, test for fungal infection, check for underlying conditions like psoriasis, and refer you for imaging if a bony growth is suspected. Most cases of curling nails are treatable, and the earlier you address them, the less likely you are to need a surgical solution down the line.
Medications That Can Alter Nail Shape
Certain drugs are known to affect how nails grow. Beta-blockers, used for high blood pressure and heart conditions, have been reported as a cause of pincer nail formation, likely because they reduce blood flow to the extremities. Some chemotherapy agents cause dramatic nail changes, including curling, thickening, and sometimes temporary nail loss. Retinoids, used for severe acne and certain skin conditions, can thin the nail plate and alter its curvature. If your nails started curling after beginning a new medication, mention the timing to your prescribing doctor. Stopping or switching the drug sometimes allows the nail to grow out normally over several months, though this is a decision that has to weigh the nail problem against whatever the medication is treating.