Ingrown toenails develop when the edge of a nail, usually on the big toe, curves or grows into the soft skin beside it. This affects roughly 2.5% to 5% of the population, and the causes range from how you trim your nails to the shoes you wear to the shape of the nail you inherited. Most cases are preventable once you understand what triggers them.
What Happens Inside the Toe
The nail plate normally sits inside a shallow groove along each side of the toe. When something disrupts that fit, a sharp edge or sliver of nail gets gradually pushed into the skin of the groove. Once the nail breaks through the outer layer of skin, the body treats it like a foreign object. The area becomes red, swollen, and painful as inflammation kicks in. If left alone, the wound can start producing pus and eventually form a mound of raw, reddish tissue called granulation tissue along the nail edge.
This progression tends to happen in three recognizable stages. First, the skin alongside the nail becomes swollen, red, and tender to the touch. Second, the area begins to leak fluid or discharge. Third, that excess granulation tissue builds up around the embedded nail. Catching it at stage one makes home care much more effective. By stage three, you’re typically looking at a visit to a podiatrist or doctor.
Trimming Mistakes Are the Top Cause
The single most common reason people get ingrown toenails is cutting their nails wrong. Rounding the corners of the nail, or tapering the edges to match the curved shape of the toe, leaves a short, angled edge that the surrounding skin can easily grow over. As the nail regrows, it pushes directly into that skin instead of growing straight out past it. Cutting nails too short has the same effect: the skin at the tip folds over the shortened nail, and the regrowing edge digs in.
The fix is straightforward. Cut your toenails straight across the top so the corners remain visible and extend slightly beyond the skin on each side. Resist the urge to shape them into a curve. Use clean, sharp nail clippers rather than tearing or picking at the nail, which can leave jagged edges that act as tiny spikes against the skin groove.
Shoes That Squeeze the Toes
Tight footwear is the second major contributor. When a shoe’s toe box is too narrow, it presses the big toe against the second toe, creating constant sideways pressure on the nail. That pressure pushes the nail edge into the skin groove with every step. Over hours of walking, this repeated compression causes inflammation and pain, and it can force the nail to grow at an abnormal angle.
Pointed-toe dress shoes, high heels, and narrow athletic cleats are the most frequent offenders. Soccer cleats deserve special mention: they tend to run narrow, and the sport itself involves repeated impact to the toes from kicking. The more trauma the nail sustains over time, the more the nail curves inward, increasing the odds of it becoming ingrown. Ballet shoes and other tight performance footwear create similar problems.
If you’re prone to ingrown toenails, choosing shoes with a roomy toe box is one of the simplest changes you can make. Your toes should be able to wiggle freely, and there should be no pressure on the sides of your big toenail when you’re standing.
Genetics and Nail Shape
Some people are simply born with nails that curve more sharply than average. A condition called pincer nail causes the nail to develop an exaggerated sideways arch that gets more pronounced toward the tip of the toe, squeezing the skin beneath it. This trait can run in families with an inherited pattern, meaning if a parent or grandparent had unusually curved nails or chronic ingrown toenails, you may be more likely to deal with the same problem.
Wider nail plates, naturally thick nails, and unusually shaped nail grooves can all shift the balance toward ingrown nails regardless of how carefully you trim. If your nails seem to curve inward no matter what you do, genetics is likely playing a role, and you may benefit from professional nail care rather than trying to manage them at home.
Injury and Repetitive Trauma
A single injury, like stubbing your toe hard or dropping something on it, can damage the nail bed and alter how the nail grows back. But repetitive, lower-grade trauma is just as common a trigger. Runners, soccer players, and hikers put sustained pressure on their toenails with every stride. Over weeks and months, that microtrauma gradually changes the nail’s curvature and pushes it into the surrounding skin.
Any activity that involves sudden stops, pivoting, or repeated toe impact increases risk. This includes basketball, tennis, and dance. Even long walks in poorly fitting shoes can generate enough friction to set the process in motion. Keeping nails trimmed short (but not too short) and wearing well-fitted, activity-appropriate footwear are the best defenses for active people.
Sweat, Moisture, and Hygiene
Feet that stay damp for long periods have softer skin around the nails. Soft, waterlogged skin is easier for a nail edge to penetrate. People who sweat heavily, wear non-breathable shoes, or spend long hours on their feet in warm environments tend to experience ingrown nails more often. Keeping feet clean and dry, changing socks when they get damp, and choosing moisture-wicking materials all help reduce this risk.
When an Ingrown Nail Gets Infected
Once a nail edge breaks through the skin, bacteria have a direct path into the tissue. The most common culprit is Staphylococcus aureus, the same bacteria behind staph infections elsewhere on the body. Signs that an ingrown toenail has progressed to infection include skin that feels warm to the touch, increasing redness that spreads beyond the nail fold, and pus (a thick, white-to-yellow fluid) building up under or alongside the nail. In some cases, a visible abscess forms.
An untreated nail infection can cause the nail itself to grow abnormally, developing ridges or a yellowish-green discoloration. In severe cases, the nail may become dry and brittle, separate from the nail bed, and eventually fall off. For most healthy people, a mild infection responds well to warm soaks and proper wound care, but significant pus, spreading redness, or worsening pain usually calls for medical treatment.
Why Diabetes Raises the Stakes
People with diabetes face a compounding set of risks that turn an ordinary ingrown toenail into a potentially serious problem. Diabetic neuropathy (nerve damage in the feet) can reduce sensation, so a nail digging into the skin may go unnoticed for days or weeks. Meanwhile, diabetes weakens the immune system’s ability to fight off skin infections and damages blood vessels, reducing blood flow to the feet. That means any wound heals more slowly, giving an infection more time to spread. In the worst cases, untreated foot infections in people with diabetes can lead to tissue death and require aggressive medical intervention.
For anyone managing diabetes, checking your feet daily for redness, swelling, or changes around the toenails is an important habit. Many people with diabetes see a podiatrist regularly for routine nail trimming specifically to avoid this kind of complication.
Preventing Ingrown Toenails
Most ingrown toenails come down to a handful of controllable factors. Trim your nails straight across, leaving the corners intact and the edge roughly even with the tip of the toe. Wear shoes that give your toes room to move. Replace worn-out athletic shoes before they start compressing your toes. If you play sports that involve kicking or sudden stops, make sure your cleats or sneakers fit properly and aren’t too tight in the toe box.
Avoid picking at your nails or tearing them instead of cutting them. Keep your feet dry by changing into fresh socks after exercise or heavy sweating. If you notice early signs of an ingrown nail (tenderness and redness along the edge), soaking the foot in warm water for 15 to 20 minutes several times a day can soften the skin and help the nail grow past the fold before things escalate.