Why Do Ingrown Toenails Occur?

One of the biggest misconceptions about ingrown toenails is that they are always caused by cutting the nail incorrectly. While poor nail trimming can certainly contribute in some cases, modern research and clinical experience show that the development of an ingrown toenail is usually far more complex. In most patients, several factors combine to place excessive pressure between the edge of the nail and the surrounding skin.

Understanding these contributing factors is important because successful treatment involves more than simply removing the painful portion of the nail. Whenever possible, treatment should address the underlying cause to reduce the risk of the problem returning.

Natural Nail Shape

One of the strongest risk factors is simply the natural shape of the toenail.

Some people are born with relatively flat nails, while others naturally have nails that are much more curved from side to side. Highly curved nails place greater pressure on the skin folds beside the nail. As the nail grows forward, its edges are more likely to dig into the surrounding tissue, particularly when additional pressure is applied from footwear or physical activity.

This inherited tendency explains why ingrown toenails often run in families. Although lifestyle factors remain important, genetics frequently influence the overall shape of the nail plate and surrounding soft tissues.

The Shape of the Toe

Not only does the nail vary between individuals, but so does the shape of the toe itself.

Some people naturally have prominent nail folds that sit closely against the nail plate. Even if the nail grows normally, these soft tissues may be repeatedly compressed against the nail edge during walking. Over time, this constant pressure can produce inflammation and eventually allow the nail edge to penetrate the skin.

Footwear

Shoes are often blamed for ingrown toenails, and in some cases they do play an important role.

Footwear that is too narrow through the toe box compresses the toes together, increasing pressure along the edges of the nail. Repeated compression over many hours each day may gradually push the surrounding skin against the nail until irritation develops.

This is commonly seen in:

• safety boots
• school shoes
• football boots
• cycling shoes
• high heels
• narrow fashion footwear

However, it is important to remember that footwear alone rarely explains the entire problem. Many people wear the same shoes for years without developing an ingrown toenail, while others develop one despite wearing sensible footwear. Shoes are therefore best considered one contributing factor rather than the sole cause.

Trauma

Injury is another recognised cause.

A single heavy object falling onto the toe may damage the nail and alter the way it subsequently grows. More commonly, repeated minor trauma gradually irritates the nail over time. Sports involving running, football, hiking, tennis or dancing repeatedly load the toes and may contribute to ingrown toenails in susceptible individuals.

Even repeated pressure from stopping abruptly inside footwear while walking downhill can irritate the nail over many months.

Incorrect Nail Cutting

Although nail cutting is not responsible for every ingrown toenail, it remains an important factor.

Many people cut deeply into the corners of the nail in an attempt to remove the painful edge. Unfortunately, this often creates a sharp spike of nail hidden beneath the skin. As the nail continues growing forward, this spike may act like a tiny spear that repeatedly penetrates the surrounding tissue.

For this reason, repeatedly "digging out" the corner often provides temporary relief while increasing the likelihood of future recurrence.

Similarly, excessively shortening the nail may allow the surrounding skin to fold over the end of the nail, making it easier for the nail edge to become embedded as it regrows.

Sweating and Skin Changes

Excessive sweating can soften the skin around the nail, making it more vulnerable to injury from the nail edge.

This is one reason teenagers and young adults, who often sweat more than older adults, commonly present with ingrown toenails.

Conversely, some older patients develop thickened or less elastic skin around the nail that may also contribute to abnormal pressure.

Rapid Growth During Adolescence

Ingrown toenails are particularly common during adolescence.

Teenagers often experience rapid nail growth, increased participation in sport, hormonal changes affecting sweating and prolonged use of enclosed footwear. These factors combine to make adolescence one of the most common periods for developing an ingrown toenail.

Previous Surgery

Occasionally, previous nail surgery itself contributes to recurrent problems.

If the procedure did not completely destroy the portion of nail responsible for the problem, a narrow spike of nail may regrow. This residual nail can become even more problematic than the original ingrown toenail because it is often hidden beneath scar tissue.

This is why recurrent ingrown toenails following previous procedures require careful reassessment rather than simply repeating exactly the same treatment.

Multiple Factors Usually Work Together

Perhaps the most important concept is that ingrown toenails are multifactorial.

Rarely is there one single cause. More commonly, a naturally curved nail, combined with tight footwear, repeated sporting activity and a small amount of incorrect nail trimming, eventually produces enough pressure to initiate the problem.

Understanding these contributing factors helps explain why treatment should be individualised rather than assuming every patient requires exactly the same approach.

Evidence Update

Current research recognises ingrown toenails as a multifactorial condition. Genetics, nail anatomy, biomechanics, footwear, trauma and environmental factors all contribute to varying degrees. Modern management therefore focuses on identifying the individual factors responsible rather than assuming there is a single universal cause.

Patient Tip

Avoid repeatedly cutting down the corners of the nail to "dig out" the painful edge. This commonly leaves a hidden nail spike that can make the problem worse as the nail grows.