Thick toenails can be unsightly and cause discomfort. Fungal infections, older age, psoriasis, and other factors can cause toenails to thicken. Treatment depends on the severity of nail changes and the underlying cause.

There are many potential causes of thick nails. By understanding the causes, a person may be able to prevent thick nails from forming and treat them quickly if they do develop.

  • Fungal infection is a common cause of thick nails.
  • If nails unexpectedly change in thickness, color, or texture, it is important to consult a doctor to rule out underlying conditions.
  • People can often prevent thick nails by avoiding infections and irritants, and keeping nails dry.

This article examines the causes, symptoms, prevention, and treatment options for thick fingernails and toenails.

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Fingernails and toenails act as a strong barrier between the soft tissue of the nail bed under them and the environment beyond.

Fingernails are useful for daily tasks, such as scratching an itch. They also assist with the sensory functions of the fingers, providing a hard contrast against the softer skin of the fingertip.

As a person ages, their nails can start to break down, or they may develop a condition that causes thick nails to form.

Although there are many potential causes of thick nails, a fungal infection is the most likely cause in the toenails.

Other conditions, such as psoriasis or diabetes, may also cause thick nails to develop.

The exact cause of thick nails will help decide a person’s treatment to correct the condition.

A person may overlook thick toenails in the early stages. However, as the nails get more obviously thicker, they may notice several symptoms, including:

  • brittle, easy-to-break nails
  • bad odor from the nail
  • nails lift easily from the nail bed or do not seem fully attached to the nail bed
  • cutting or trimming is difficult
  • splitting or cracking of the nail occurs easily
  • dirt or other debris gets under the nails
  • pain or discomfort

As the toenails thicken, they may appear rough, ridged, or scaly on the surface.

The nails may also take on a yellow, green, or brown hue.

There are various reasons why nails may thicken. Many of the causes relate to either infections or other medical conditions connected to nail thickening.

Some of the most common causes are listed below:

Fungal and yeast infections

Primarily, fungal and yeast infections affect a person’s toenails rather than fingernails.

A type of fungal infection called onychomycosis is one of the most common causes of thick nails.

Fungal infections often grow in toenails because they thrive in warm, moist environments. They are easily spread and can develop quickly, causing many of the symptoms described above.

Some people are more prone to fungal infections than others. Some of the leading causes of fungal infections in the toenails include:

  • constant exposure to wet areas
  • smoking
  • constrictive footwear
  • damage to or next to the nail

In addition, some health conditions can increase the risk for fungal nail infections, such as:

To help prevent fungal infections, people should avoid walking around barefoot in public places, especially locker rooms and showers. It is also important to keep footwear dry.

Doctors do not usually consider fungal nail infections to be serious. These infections can often improve with treatment.

It is not always possible for the nail to return fully to its prior appearance. But treating the fungal infection can help a person reduce discomfort and improve the look of the nail.


Toenails can thicken as a result of sudden or repeated trauma or injury. Mostly, this happens to people involved in sport or exercise, such as soccer players, runners, and dancers. It can also affect people who wear ill-fitting shoes.

Often, thick nails due to injury are mistaken for fungal infections.

Seeking medical treatment for a nail injury may help the nail to grow back more normally. If treatment helps, the improvement is likely to happen slowly. It takes months for new nail growth to fully replace the length of the nail.

Yellow nail syndrome

This less-common cause of thick nails affects both fingernails and toenails. The condition causes the nails to yellow and become curved and thickened.

A person with yellow nail syndrome typically experiences respiratory problems and swelling in the arms and legs. This is due to a buildup of fluid around the lungs and in the limbs.

Although doctors do not know the exact cause of yellow nail syndrome, some believe there could be a genetic connection. The condition may also be associated with some cancers and immune disorders.

There is currently no cure for yellow nail syndrome, and treatments for affected nails have limited effectiveness.


Psoriasis is an autoimmune disorder that typically causes red, scaly patches on the skin. Psoriasis of the nails often accompanies the condition, affecting both the fingernails and toenails.

In addition to thickening, psoriasis can also cause changes to the nail, such as:

  • discoloration
  • lifting from the nail bed
  • pitting

People with nail psoriasis may have symptoms that come and go intermittently. Treatment can reduce inflammation and improve the condition of the nails over time, but healing is usually a slow process.


Paronychia is inflammation that causes redness and swelling of the skin around the nail. Inflammation of the nail area over a long period of time is known as chronic paronychia. This can be caused by infections or exposure to irritants, such as cleaning solutions.

Over time, both fingernails and toenails may become thick. A person may notice that layers of the nail start to peel off.

People can develop paronychia from frequently sucking on their fingers, dishwashing, and trimming the nails or cuticles too much.

Several occupations are also more of a risk for developing thick nails due to paronychia. These jobs include:

  • dishwashers
  • bartenders
  • laundry workers
  • cleaners
  • cooks
  • nurses
  • fishers

The condition usually affects multiple fingers or toes. Chronic paronychia can be managed by:

  • avoiding contact with irritants
  • treating inflammation
  • allowing the nail’s natural barrier to heal over time


Often, as a person ages, the nails on their toes start to thicken. Though the condition is most common on the toenails, it is also possible for the fingernails to thicken.

Healthcare professionals believe that the nails thicken as people get older due to changes to blood circulation or long-term UV exposure.

The thick nails and the ridges that form on the nail due to aging are not treatable. However, a person can buff them slightly to smooth their appearance.

Other causes

Rare causes of thickened nails include the following:

Thick nails are often the symptom of another infection or disorder.

In most cases, thick nails are unlikely to cause further complications. But if left untreated, they can continue to worsen, may cause pain, and may make wearing footwear uncomfortable. Severely thick fingernails may cause some loss of dexterity in the hands.

Seeking a medical diagnosis for thick nails can help to prevent other complications that could arise. For example, a person may need treatment for an underlying condition that is affecting the health of the nails, such as diabetes.

People can prevent some causes of thick nails. Thick nails are less likely to happen if hands and feet are kept clean and dry, with nails clipped short.

Nail infections can enter the nail through cuts or cracks in the surrounding skin. Individuals can avoid some nail infections by keeping hands and feet moisturized to prevent cracks and treating cuts or other skin issues.

To prevent thick nails, a person should avoid the following situations:

  • working in wet environments without gloves
  • sharing nail clippers
  • sharing towels
  • walking barefoot in public areas such as the locker room or shower at the gym

People should always wear gloves while working in a wet area, such as dishwashing.

Anyone who visits nail salons should learn about licensing and certification for these businesses. Licensing may differ by state. It is important to choose a reputable nail salon that follows all necessary sanitation practices. Manicure and pedicure instruments must be properly sterilized between uses to avoid spreading nail fungus or other infections.

Other prevention tips include:

  • wearing well-fitting shoes
  • keeping socks and shoes dry

Since underlying conditions often cause thick nails, a person should consult a doctor if they notice their fingernails or toenails thickening or changing color or texture.

Conditions that cause thick nails may require treatment. If a known underlying condition is the cause, a doctor may wish to review the person’s existing treatment plan.

People who experience yellow, thickened nails without knowing the reason should talk with a doctor to ensure it is only a fungal infection and nothing more serious. Nail fungus can be persistent, so those who wish to treat it should start as early as possible.

A doctor will ask about a person’s medical history and symptoms and examine the nails. If their thick nails are due to an underlying condition, the doctor may prescribe further therapies to help address the new symptom.

For those with fungal infections, the doctor may need to swab under the nail or take a clipping to test for fungal growth. It is important to diagnose a fungal infection early, to improve the chances of curing the condition.

Thick nails do not always require treatment. In instances where aging is causing a person’s toenails to thicken, the treatment will likely be as simple as buffing the rough surfaces to smooth them.

In other cases, a doctor will need to prescribe treatment. The goal may be to improve the condition of the nail or prevent it from worsening.

Treatment options for thick nails include:

  • prescription creams or ointments
  • oral medications
  • laser therapy or light therapy
  • injections
  • surgery to remove the nail and allow it to regrow

A doctor will choose the appropriate treatments based on the cause of the thickened nails.

In some cases, the cause of thick nails may be benign, such as aging. In other cases, a person will require treatment to address the underlying condition.

Thick nails can sometimes be a sign of other health concerns. It is important for people to seek medical advice and treatment when they notice thickening or discoloration of the nails. If left untreated, thick nails can worsen over time.

By avoiding irritation and infection of the nail area, a person can often prevent nail thickening.

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