What causes nail fungus? Diagnosis, prevention, and treatment

Medically reviewed by Marquissa Beverly, DPM, MHA
Podiatrist
Updated Jun 10, 2024  •  Published Jun 2, 2023
Datos Verificados
In this article:

Overview: What is nail fungus?

Nail fungus is a common infection found in the fingers and toes, but toenail fungus appears more prominent than fingernail fungus. Fungal nail infections are also known as tinea unguium or onychomycosis. When the fungal infection causes a skin infection, this is known as tinea pedis, commonly referred to as athlete’s foot. Usually, the fungal organism comes into contact with the skin after a cut or injury occurs close to the nail. An example would be a cut to the nail’s cuticle. This provides a portal for the organism to infect the nail. 

There are millions of different fungi responsible for nail fungus. The most common is dermatophyte, but yeasts (Candida albicans) and molds are other common fungi that may infect the nail.

Once the infection occurs, the nail becomes thicker, discolored, develops an abnormal shape, and turns brittle. In more severe cases, the nail may become painful or even cause a foul odor. Occasionally, the surrounding skin may become secondarily infected with bacteria, causing cellulitis in the toe. It is essential that these nail changes are not ignored, as severe nail fungus may result in the need for the infected nail to be surgically removed, or sometimes there may be permanent damage to the nail itself.

Key takeaways:

  • Nail fungus is a common health condition that can affect anyone regardless of age, sex, race, or ethnicity. According to the Centers for Disease Control and Prevention (CDC), and more than 3 million cases of fungal nail infections are reported in the United States annually.

  • Nail fungus is caused by tiny microscopic fungi, most commonly dermatophytes. The organism infects the nail by either getting into a small cut close to the nail, a crack in the nail, or a separation of the nail.

  • Risk factors for nail fungus include aging, living in hot and or humid environments, with weakened immune systems, a history of athlete’s foot, and certain lifestyle choices (barefoot walking, hands and feet that are constantly wet, those who smoke, use of plastic gloves, wearing tight-fitting shoes).

  • Symptoms of nail fungus include discoloration of the nail that may start as white spots but also turn yellow, brown, or green. Thickening of the nail may occur with a buildup of debris underneath the nail plate. Nails may be crumbly or split. In severe cases, the nail may separate from the nailbed altogether.

  • Nail fungus is typically self-diagnosable but may occasionally require a medical diagnosis as other nail conditions look similar to a fungal infection of the nails.

  • Nail fungus generally requires treatment. It typically resolves after treatment for 4-6 months for fingernails and 12-18 months for toenails, according to the American Academy of Dermatology.

  • Treatment of nail fungus may include home remedies, topical treatments, oral antifungals, laser treatment, and, in some rare cases, nail removal. Read more about nail fungus treatments.

  • Nail fungus is preventable by wearing protective shoe gear while walking in warm, moist places (i.e., locker rooms, beaches, swimming pools, and public showers), maintaining nails by keeping them clean and trimming them in shorter lengths, keeping socks, and shoes, hands, and feet clean and dry daily, wearing comfortable shoes that are not too snug, sanitizing utensils such as nail clippers after each use, and treating any surrounding athlete’s foot that may co-exist.

  • Use coupons for nail fungus treatments like Loprox (ciclopirox), Jublia (efinaconazole), and Lamisil (terbinafine) to save up to 80%.

What causes nail fungus?

  • Nail fungus is caused when a type of fungus (yeast, molds, but mostly dermatophytes) enters the nail bed. This may be from skin-to-skin contact with someone who has athlete's foot or ringworm on the hands. 

  • If the skin is cut close to the nail, the organism can enter. The skin may crack when it is extremely dry or an athlete’s foot condition is present. This allows the fungus to invade the nail and infect it.

  • The fungus may also enter if there is a crack in the nail or the nail has separated from the finger or toe, usually due to trauma or injury. Nail injuries can occur when nails are too long, or shoes are too tight.

  • Other causes may be from hands and feet constantly being wet and moist. This is usually seen while walking barefoot in warm, humid environments (pools, locker rooms, and gyms) where fungus thrives, or the hands remain wet from pools, constant washing, or gardening.

  • Causes of nail fungus are also related to using contaminated supplies such as nail clippers, nail polish, towels, shoes, and socks.

Risk factors for nail fungus

  • Weakened immune system (cancer and organ transplant patients, AIDS, HIV)

  • Smokers

  • Older adults

  • Diabetes

  • Poor circulation (PVD)

  • Athlete's foot (tinea pedis)

  • Psoriasis

  • Family members living with onychomycosis

  • Barefoot walking in hot/humid environments 

  • Nail injury

  • Nail infection/paronychia

  • Improper shoe gear

  • Professions where hands and feet are constantly wet or get sweaty

  • Frequent visits to the nail salon for manicures and pedicures

  • Sedentary lifestyle

  • Improper diet

  • Family history of fungal infections

  • Previous history of a healed fungal infection

Is nail fungus serious? When to see a doctor

Nail fungus is not life-threatening. Most people are just not pleased with the way it looks. It is quite easy to develop, and about 14% of the population has suffered from this type of fungal infection at least once. Anyone can develop nail fungus. However, those in older demographics with certain health conditions, professions, or hobbies may be more at risk of developing this nail condition.

Unfortunately, nail fungus will rarely go away on its own. The faster the nail condition is treated, the better the chances are of curing this stubborn infection. Occasionally, home remedies can be used to treat mild cases of nail fungus. If the symptoms are not improving in a few months or nails have become painful, it is best to seek medical attention from a healthcare provider. When nail fungus is ignored, it may cause permanent damage to the nails.

How is nail fungus diagnosed?

In order to properly diagnose nail fungus, one must be seen by a qualified healthcare provider, such as a podiatrist or dermatologist. The specialist will take a thorough history and perform a physical examination. They will ask if there are any current medications that are being used, how long the condition has existed, and if any treatments have already been attempted. A nail biopsy may also be performed to help confirm if the nail condition is indeed caused by a fungus. A nail biopsy can also determine what type of nail fungus is occuring. By taking a portion of the nail or surrounding skin, the nail or skin is examined with a microscope for fungal properties. This is done because there are other medical conditions (i.e., yellow nail syndrome, drug reactions, thyroid problems, nail trauma, nail malignancy, psoriasis, and eczema) that may also be responsible for nail changes.

Is nail fungus contagious? 

It is important to know that nail fungus is contagious. When sharing contaminated supplies (nail clippers, nail polish), towels, socks, and shoes, can place someone at risk of developing a nail fungus. Also, walking barefoot at public pools, locker rooms, and gym floors can cause cross-contamination, as people with the infection may spread their fungus on these surfaces. Wear shoes such as flip-flops or shower shoes to protect the feet in public places. Always use personal supplies to ensure things are properly cleaned and sanitized. Never share personal items when possible.

Is nail fungus curable?

The good news is that nail fungus is a very curable condition. In order to get rid of nail fungus, it must be treated. Ignoring the problem by covering it with nail polish or acrylic nails will not get rid of the infection. If the infection is not treated, it can spread to adjacent nails, surrounding skin, and even become painful. The appropriate treatment plan will be developed by a doctor. This usually includes topical antifungals (Jublia, Kerydin, Loprox), oral antifungal medications (Diflucan, Lamisil, Sporanox), laser therapy, or possible nail removal. The specialist will give specific instructions on how to take antifungal medication and for how long. It is important to complete the medication since symptoms may improve before the infection is entirely gone. The new nail must grow without any remaining infection for the fungus to cure completely.

How to prevent nail fungus

The best way to cure nail fungus is to prevent it from happening in the first place. Simple steps such as cleaning used socks and towels daily and always cleaning nail utensils after each use may go a long way toward preventing the spread of fungal organisms on the nails. Certain jobs and hobbies may require special moisture-wicking socks, foot sprays or powders, or special gloves or waterproof shoe gear to help keep the nails dry. Starting with a healthy diet and lifestyle also plays a large part in wellness, healing, and preventing infections in general.

RELATED: Foot fungus treatment and prevention

Most importantly, nail fungus is curable if diagnosed early

It is important to know that nail fungus will not just go away. Ignoring the problem will only make the condition worse. 

Nail fungus is most commonly caused by dermatophytes thriving in warm, moist environments such as sweaty feet and hands. People of more advanced age, immunocompromised, or constantly working in wet, hot environments are more at risk of developing nail fungus. 

It is important to identify if the nail changes are due to a fungal infection or some other reason. If the changes are caused by a fungus, the infection can spread to other nails and surrounding skin if left untreated. This makes the condition harder to treat. If the infection gets too severe, the nail changes may become irreversible. 

As soon as changes to the nail have been identified, seek the advice of a doctor. This condition is very treatable if steps are taken to treat it as soon as possible. A healthcare professional will be able to determine if nail fungus is present and the best type of treatment options due to medical history, lifestyle, and severity of the infection. Both prescription and over-the-counter medications are available for nail fungus.

FAQs about nail fungus causes

What deficiency causes nail fungus?

There has been a link between biotin and vitamin D deficiency and the development of nail fungus and plate discoloration. More research is needed to be certain that these are the true causes.

Do toenail fungal infections indicate other health problems?

Nail fungus can infect anyone. However, nail fungus is more common in those with weaker immune systems from certain medical conditions such as diabetes, cancer, HIV, and AIDs.

Why am I prone to fungal infections?

Many risk factors play a role in someone developing nail fungus. Most are lifestyle choices where the hands and feet are constantly in warm, moist environments. If a weakened immune system is involved, there may be a higher chance of developing nail fungus, as the body will have a more challenging time fighting off the infection than those with a stronger immune system. Occasionally, those with a family history of fungal nail infections may also be at higher risk for developing nail fungus.

What’s next? Additional resources for people with nail fungus

Test and diagnostics

Treatments

Scientific studies and clinical trials

Medically reviewed by Marquissa Beverly, DPM, MHA
Podiatrist

Marquissa Beverly, DPM, MHA, graduated from Barry University School of Podiatric Medicine. She completed her three-year surgical training of the foot and ankle at South Miami Hospital. Dr. Beverly has 12 years of clinical and surgical experience in the lower extremity. She lives in the Tampa Bay area with her family, where she works in private practice. Her passion is patient advocacy through education so that people may be active participants in their own health care. As a medical writer and reviewer, Dr. Beverly feels this allows her to reach more people to help them live healthier lives.

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