Ingrown toenails develop when the edge or corner of a nail grows into the soft skin beside it, triggering pain and inflammation. The big toe is the most common site. While the immediate cause is always the same (nail pressing into flesh), several factors determine whether it happens to you, from how you trim your nails to the shape of your nail bed itself.
Trimming Technique Is the Most Common Trigger
The single biggest reason people get ingrown toenails is cutting them too short or rounding the corners. When you curve the edges of a toenail, the skin at the sides can fold over the shortened nail edge. As the nail grows back, it pushes directly into that skin fold instead of growing over it. The same thing happens when you cut nails into a V-shape at the center, a common but counterproductive attempt to “guide” growth away from the edges.
The correct technique is simple: cut straight across, leaving the nail long enough that the corners sit loosely against the skin on either side. You want a clean, flat edge with no rounded corners. If the white tip of the nail is completely gone after trimming, you’ve gone too short.
Tight Shoes Push the Nail Into Skin
Shoes with a narrow toe box compress the toes together, forcing the big toe against the second toe. That sustained pressure pushes the nail edge into the surrounding skin. The combination is especially problematic: trim your nails short, then spend all day in tight shoes, and the nail has nowhere to grow except into softened, compressed tissue.
When choosing shoes, your toes should be able to wiggle freely. If the front of the shoe pinches or your toes overlap, the fit is too tight. This applies to athletic shoes, work boots, and dress shoes alike. High heels are a frequent offender because they shift body weight forward, cramming the toes into the tapered front of the shoe.
Some People Are Genetically Prone
Not everyone who trims their nails poorly or wears tight shoes develops ingrown toenails, and some people get them repeatedly despite doing everything right. The difference often comes down to inherited nail shape. Some people are born with nails that curve more sharply at the edges, making them naturally more likely to dig into the surrounding skin.
A more extreme version of this is called pincer nail deformity, where the nail thickens and the edges curl dramatically downward into the nail fold. Research tracking multiple generations of affected families suggests this trait follows an autosomal dominant inheritance pattern, meaning if one parent has it, roughly half their children will too. These cases were documented across three generations in one family, with symptoms appearing in the teens and early twenties. The underlying problem is a mechanical one: the nail bends inward because the normal upward forces that keep a flat nail shape are either absent or overpowered by increased curving force.
Injury, Sweat, and Other Risk Factors
Stubbing your toe hard, having it stepped on, or dropping something on it can shift the nail plate or crack the edge, creating a sharp fragment that grows into the skin fold as it recovers. Athletes who repeatedly jam their toes against the front of their shoes (runners, soccer players) face this risk chronically rather than from a single event.
Excessive sweating plays a less obvious role. Moisture softens the skin around the nail, making it easier for the nail edge to embed itself. That softened, damp environment also makes infection more likely once the nail breaks through the skin. Keeping feet dry and changing socks when they get damp reduces this risk.
Why Diabetes Makes Things Worse
People with diabetes face a compounding set of problems when it comes to ingrown toenails. Nerve damage in the feet (a common complication of diabetes) reduces sensation, so an ingrown nail that would cause immediate pain in a healthy person can go unnoticed for days or weeks. By the time it’s discovered, the nail may have penetrated deeply and infection may already be present.
Diabetes also affects blood flow to the feet. Poor circulation thickens the nails and disrupts their structure, making them harder to trim cleanly and more prone to irregular growth. Reduced blood supply impairs the body’s ability to fight off bacteria, so even a minor ingrown nail can escalate into a serious infection. People with diabetes also tend to develop increased pressure on the forefoot and subtle changes in how they walk, which adds mechanical stress on the nail and surrounding tissue.
What Happens as It Progresses
Ingrown toenails follow a fairly predictable three-stage pattern. In stage one, the nail has grown into the skin and the area is painful, red, and swollen. Most people notice the problem here. Many mild cases resolve on their own or with home care like soaking the foot in warm water and gently lifting the nail edge away from the skin.
In stage two, the body reacts to the ongoing irritation by growing new tissue at the nail edge, called a granuloma. This inflamed tissue weeps fluid and produces pus. The area becomes increasingly tender and may bleed easily when bumped.
Stage three is chronic. The skin around the nail is persistently inflamed, oozing pus, and the granuloma tissue begins growing over the nail itself. At this point, the problem won’t resolve without professional treatment. If bacteria enter the wound, the infection can spread beyond the toe, causing fever, fatigue, and cellulitis (infection of deeper skin layers). People with weakened immune systems are particularly vulnerable to this escalation.
How Ingrown Toenails Are Treated
Mild cases often respond to conservative care at home: warm soaks, keeping the area clean, wearing open-toed shoes, and gently placing a small piece of cotton or dental floss under the nail edge to encourage it to grow above the skin. This works best when caught early, before any pus or granuloma tissue appears.
For recurring or more advanced cases, the standard procedure is partial nail avulsion, where a doctor numbs the toe and removes the offending strip of nail along the edge. The procedure itself takes only a few minutes. On its own, however, the nail edge grows back and the problem returns about 10% of the time. When the doctor also applies a chemical (phenol) to the exposed nail root to prevent that strip from regrowing, the recurrence rate drops to around 1.4%. In younger patients under 35, adding this step brought recurrence to zero in one study of 46 patients. Recovery typically involves keeping the toe clean and bandaged for a few weeks, with most people returning to normal shoes within a couple of days.
Preventing Recurrence
Once you’ve had one ingrown toenail, you’re more likely to get another, especially if the underlying cause hasn’t changed. The most effective prevention combines three habits: trimming nails straight across (never rounded or too short), wearing shoes with a roomy toe box, and keeping feet clean and dry. If you have naturally curved nails, you may need to trim more carefully and more frequently to keep the edges from reaching the skin fold. A podiatrist can show you the right technique for your specific nail shape.