What Makes Toenails Thicken? Symptoms, Related Diseases And More

Human nails have always served as the first barrier between the nail bed and the outdoors. Though they seem superficial when it comes to their purpose, they do serve another purpose in the protection of our body from some unwanted elements in the environment.

However, as people age, their nails, like every other part of the human body become more prone to breakdown and other conditions. Regarding this part of the body, there exists a condition where thick nails start to form.

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

Most people use their fingernails daily, to scratch an itch or for manual tasks, such as removing lids on jars or bottles.

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, in the toenails a fungal infection is the most common cause.

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

The exact cause of thick nails decide what treatment a person needs to treat the condition.

Thick toenails
Thick toenails/ Credit: Medical News Today

Symptoms And Appearance

Thick toenails may go unnoticed in the early stages. But as the nails get more obviously thicker, a person may notice several symptoms, including:

– brittle, easy-to-break nails
– bad odor from the nail
– nails lift easily from 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 can be felt

Also, as the toenails gradually thicken over time, they may appear gnarly with some scaling on the surface.

Often, the nails will take on a yellow, green, or brown hue.

Causes And Risk Factors

There are a variety of 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

Fungal infections develop in environments that are warm and moist and can spread quickly. Primarily, fungal infections affect a person’s toenails.

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.

To avoid fungal infections, people should avoid walking around barefoot in public places, especially locker rooms and showers, and by keeping footwear dry.

Some people are more prone to fungal infections than others. Some of the leading causes of fungal infections in the toenails include: athlete’s foot spreading to the toenail bed, constant exposure to wet areas, smoking, constricted footwear, weakened immune system,
medical conditions such as psoriasis, circulatory problems, and type 1 and 2 diabetes, damage to or next to 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, but also to people with ill-fitting shoes. Often, thick nails due to injury are mistaken for fungal infections.

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 often experiences respiratory problems and swelling in the arms and legs 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 is a strong genetic connection.


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

When psoriasis is the direct cause of thickened nails, a person is likely to develop ridges on the nails, and the nails may loosen and separate from the nail bed.


Paronychia is a skin condition that causes redness and swelling around the nail. Over time and multiple infections, both fingernails and toenails may become thick. A person may notice that layers of the nail start to peel off.

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

People with certain occupations are also more of a risk for developing thick nails due to paronychia. These jobs include dishwashers,
bartenders, laundry workers, cleaners, cooks, nurses, people who fish.


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

It is thought that the nails thicken as people get older because the body is not as able to renew itself as it was at a younger age.

The thick nails and the ridges that form on the nail as a result of aging are not treatable. They can be buffed slightly, however, to smooth out their appearance.


Thick nails are not likely to cause further complications, although, if left untreated, they will continue to worsen, may cause pain, and may make wearing footwear uncomfortable. Complications from the pre-existing conditions that caused the thick nails are, however, likely to follow. For example, thick nails may be an additional complication acquired by a person who has underlying diabetes.

When To See A Doctor

Since underlying conditions often cause thick nails, a person should consult a doctor if they notice their fingernails or toenails thickening or changing color. Someone with an underlying condition, such as diabetes or psoriasis, may well be treating it already.

People who experience yellow, thickened nails without knowing a reason for them, should talk to their doctor to be sure that it is only a fungal infection and nothing more serious.