onychocryptosis

Onychocryptosis is the medical term for an ingrown toenail, a condition where the edge of the nail plate digs into the surrounding skin fold, causing pain, swelling, and sometimes infection. It ranks among the most common nail disorders, particularly in adolescents and young adults, and can interfere with everyday activities like walking or wearing shoes.

What Actually Happens Inside the Toe

The problem starts when the nail plate injures the soft tissue alongside it, known as the nail fold. That trauma sets off a cycle of inflammation and pain, and if bacteria get involved, infection follows.¹ In many cases the body responds to the constant irritation by growing granulation tissue, the red, raw-looking bump that bleeds easily and often alarms people into seeking help. The big toe is by far the most commonly affected, though any toenail can theoretically become ingrown.

Despite how simple the condition sounds, the mechanics are not always straightforward. Sometimes the nail itself is too wide or too curved for the nail bed beneath it. Sometimes the skin fold is excessively prominent, pressing into an otherwise normal nail. And sometimes a combination of factors, such as tight footwear, aggressive nail trimming, or a stubbed toe, pushes a borderline situation into a painful one. That interplay between nail shape and surrounding tissue is why some people deal with ingrown toenails repeatedly while others never get one.

Common Causes and Risk Factors

The single most cited culprit is cutting your toenails too short or rounding the corners. When you trim the nail into a curve, the edges can grow downward into the skin instead of straight across. Tight or narrow shoes compound the issue by squeezing the toes together and pressing the nail fold against the nail edge. Sweaty feet can soften the skin around the nail, making it easier for the nail to penetrate. Trauma, whether from a sports injury, dropping something on your foot, or repetitive pressure from running, can also trigger an episode.

A prospective case-control study evaluating predisposing factors found that most of the identified risk factors were modifiable, meaning that changes in footwear and grooming habits could meaningfully reduce both new cases and recurrences.² Genetic factors play a role too: some people inherit nails that are naturally wider or more curved (a feature called pincer nail when it becomes extreme), and those nails are more prone to burrowing into the skin. Obesity, diabetes, and hyperhidrosis (excessive sweating) have all been linked to higher rates of the condition.

Stages of Severity

Clinicians typically grade ingrown toenails into three stages, though classification systems vary. In the mildest stage, the nail fold is tender and slightly swollen but not infected. The second stage adds drainage, infection, or the formation of granulation tissue. The third and most severe stage involves chronic inflammation with overgrown skin partially covering the nail, sometimes with abscess formation.

One classification system, the Mozena system, took a more measurement-based approach. By comparing the depth of the nail fold in normal versus infected toes, researchers found that a nail fold thicker than about 3 mm correlated with greater severity and suggested that any treatment should aim to bring the fold below that threshold.³ Staging matters because it directly determines which treatments are appropriate. A mildly ingrown nail that just started hurting last week calls for very different management than one that has been oozing for months.

Conservative Treatments

For mild to moderate cases, non-surgical approaches are the first line. The most traditional home remedy is soaking the foot in warm water, gently lifting the nail edge, and placing a small piece of cotton or dental floss under the corner to guide the nail over the skin fold as it grows out. This works for many early-stage cases but requires patience and consistency over several weeks.

A more structured conservative approach is orthonyxia, which involves attaching a small corrective brace or wire to the nail. The device applies gentle upward tension at the nail edges, gradually flattening the curvature and pulling the nail out of the skin fold. Studies in children have found this method to be highly effective even in advanced stages, with the advantage of being safe and carrying a low risk of complications.⁴ A retrospective study of pediatric patients treated with orthonyxia found that the average healing time was about three months, with roughly two-thirds of patients reaching complete remission within that window.⁵

Orthonyxia is particularly appealing for children and teenagers because it avoids anesthesia, incisions, and the downtime associated with surgery. It is also used in adults, though its adoption is more common in some countries (especially in Europe and parts of Asia) than in others, where surgical approaches tend to dominate clinical practice even for moderate cases.

Chemical Matricectomy

When conservative measures fail or the ingrown nail keeps coming back, the next step often involves removing the offending strip of nail and then destroying the portion of the nail matrix (the growth center) responsible for producing it. This prevents that sliver of nail from regrowing. The most common way to destroy the matrix is chemical matricectomy, where a caustic agent is applied to the exposed matrix tissue after the nail edge has been pulled out.

Phenol, at concentrations around 88%, has been the traditional chemical of choice for decades. It works well but tends to cause prolonged wound drainage and slower healing. Sodium hydroxide at 10% concentration has emerged as an alternative, with research showing it is equally effective at preventing recurrence while allowing faster tissue recovery.⁶ A three-arm comparison study testing phenol, sodium hydroxide, and 90% trichloroacetic acid (TCA) found that TCA was associated with the least post-procedure pain and the fastest wound healing, with no recurrences at one year in any of the three groups.⁷

The appeal of chemical matricectomy is that it is a relatively quick office procedure, typically done under local anesthesia, with most people able to walk out the same day. The trade-off is that healing can take several weeks, during which the toe oozes a clear to yellowish drainage that often worries patients but is a normal part of the process. The nail permanently narrows by a few millimeters on the treated side, which most people find cosmetically acceptable and far preferable to recurring pain.

Surgical Approaches

For severe or recurrent cases, a range of surgical techniques exists. These fall broadly into two categories: procedures that alter the nail plate and procedures that reduce the surrounding soft tissue.

Winograd procedure: The surgeon removes the ingrown nail border along with the corresponding matrix tissue using a scalpel, physically excising the growth center rather than chemically destroying it.
Vandenbos procedure: Instead of touching the nail at all, the surgeon cuts away the overgrown skin fold. The wound heals on its own over several weeks. An observational study of children, adolescents, and young adults found zero recurrences, a median return to school or work of seven days, and 95% of patients saying they would recommend it.⁸
Zadik procedure: Complete removal of the nail and its entire matrix, used in severe or recurrent cases where partial approaches have failed. The toe ends up without a nail permanently.

Other techniques include radiofrequency ablation, carbon dioxide laser ablation, and various soft-tissue flap procedures, each with proponents in different surgical traditions.⁹ The Vandenbos procedure has gained renewed attention in recent years because it preserves the full nail, which many patients prefer cosmetically, and its recurrence rate is exceptionally low. Its main drawback is a longer open-wound healing period: patients in the observational study mentioned above waited a median of 23 days before they could comfortably wear enclosed shoes.¹⁰

How the Treatments Stack Up

One question almost everyone asks is which treatment is “best.” The evidence suggests there is no single winner, but simple nail avulsion (just pulling out the nail without destroying the matrix) is clearly the worst option in terms of recurrence. A large network meta-analysis of 44 studies involving over 5,000 patients found that nail avulsion alone had the highest recurrence risk. Chemical matricectomy, minor surgery, conventional wedge excision, and even conservative treatment all performed comparably for preventing recurrence.¹¹ One caveat: chemical matricectomy was associated with longer healing times compared to surgical alternatives, even though recurrence and pain outcomes were similar.

A randomized trial comparing phenol matricectomy to surgical matrix excision found that phenol gave significantly lower recurrence rates after one year, with no meaningful difference in infection rates in the days following the procedure.¹² However, a broader systematic review and meta-analysis pooling eleven studies found no statistically significant difference between chemical and surgical matricectomy for recurrence prevention overall.¹³ The practical takeaway is that both approaches work well, and the choice often comes down to surgeon experience, patient preference, and how much healing time someone can tolerate.

Managing Pain During and After Procedures

Ironically, the part of ingrown toenail treatment that many people dread most is not the procedure itself but the needle used to numb the toe beforehand. A digital nerve block, the standard technique, involves injecting local anesthetic at the base of the toe. The injection stings because the toe has limited space for the fluid, causing a tight, pressurized sensation for several seconds.

Researchers have looked for ways to make this less unpleasant. One approach, a V-shaped injection technique that uses a single puncture point instead of two, achieved full anesthesia in most patients within 10 to 20 minutes and was thought to reduce the anxiety associated with multiple needle sticks.¹⁴ Another study tested whether applying numbing cream (EMLA) to the skin before the injection would reduce pain, but found no benefit: the cream did not penetrate deeply enough to reach the digital nerves, and the swelling from the injection itself seemed to amplify pain regardless.¹⁵

Post-procedure pain varies widely depending on the technique used. Chemical matricectomy with TCA tends to produce less post-operative discomfort than phenol, and procedures that leave an open wound (like the Vandenbos) involve more prolonged soreness during healing. Most patients manage well with over-the-counter pain relievers for the first few days.

Ingrown Toenails and Diabetes

For people with diabetes, an ingrown toenail is not just annoying; it can be genuinely dangerous. Diabetes impairs blood flow to the feet and dulls nerve sensation, meaning an ingrown nail can progress to a serious infection before the person even realizes how bad it has gotten. In diabetic patients, onychocryptosis can serve as a trigger for ulceration, deep infection, and in worst-case scenarios, amputation.¹⁶

This is why diabetes care guidelines emphasize regular foot examinations and prompt treatment of even minor nail problems. If you have diabetes and notice redness, swelling, or drainage around a toenail, treating it as urgent rather than waiting to see if it resolves on its own is the safest approach. Podiatric care should ideally involve coordination with an endocrinologist or diabetes team, particularly if blood sugar control is poor, since healing after any procedure is slower when glucose levels are elevated.

When It Might Not Be an Ingrown Nail

Not every painful, swollen big toe is onychocryptosis. A few conditions can mimic the appearance of an ingrown nail closely enough to fool both patients and clinicians. One is subungual exostosis, a bony growth beneath the nail that pushes the nail upward or sideways, causing pain and sometimes distorting the nail shape in a way that looks exactly like an ingrown nail with hypertrophied skin folds. Case reports describe patients, including children, whose nail dystrophy was attributed to ingrown nails until imaging revealed the bony spur underneath.¹⁷

Pincer nails, where the nail curves dramatically inward on both sides like a tube, are a related but distinct condition. Though they can cause ingrown-nail-like symptoms, pincer nails involve the entire nail structure rather than just one edge, and their management sometimes differs. Chronic paronychia from pincer nails can, in rare cases, progress to bone infection (osteomyelitis) of the underlying finger or toe bone.¹⁸ Other mimics include fungal nail infections that thicken and distort the nail, tumors beneath the nail (including melanoma, though rare), and paronychia from causes other than nail impaction. If an ingrown nail does not respond to standard treatment, or if the presentation is unusual, imaging or a biopsy may be warranted to rule out something else.

Prevention

The single most effective preventive measure is cutting your toenails straight across rather than rounding the edges. Leave the nail slightly longer than the tip of your toe, and resist the urge to dig into the corners. Use proper nail clippers or nippers rather than scissors, which tend to encourage curved cuts.

Footwear matters more than most people realize. Shoes with a narrow toe box compress the toes and push the skin folds into the nail edges. If you spend long hours on your feet, shoes with a roomy toe area and breathable material reduce both pressure and moisture. Athletes, especially runners and soccer players, are at elevated risk because of repetitive toe trauma and sweating inside tightly laced shoes. Keeping feet dry and changing socks when they become damp helps maintain the integrity of the skin around the nail.

If you have had an ingrown toenail before, you are more likely to get one again. Recurrence rates after simple nail avulsion are high, which is why definitive treatment (chemical or surgical matricectomy) is recommended for people who keep having the same problem. For those with naturally wide or curved nails, periodic orthonyxia or routine podiatric care can keep the nail growing in the right direction and avoid the cycle of inflammation and infection that makes each episode worse than the last. Since most risk factors are within your control, small changes to grooming and shoe habits can prevent a disproportionate amount of suffering.¹⁹