Toenail Fungus (Onychomycosis): Causes and Treatments

According to the Centers for Disease Control and Prevention (CDC), fungal nail infections are common, with around 14% of the population affected.

Toenail fungus can result in discoloration of the nail and other effects on its appearance. In this article, we’ll go into detail about what toenail fungus is, what causes it, and how to treat it (or prevent it in the first place).

What is Toenail Fungus?

Toenail fungus or onychomycosis is a fungal infection of nails that leads to a steady destruction of the nail plate and can cause toenail discoloration.

While fungal infections generally result in a white or yellow discoloration of the nail, sometimes the nail can turn black due to a buildup of debris. Fungal infections are far more common in toenails than fingernails.

While many regard toenail fungus as a cosmetic issue, if left untreated it could lead to more serious health complications such as cellulitis — an infection of the deeper layers of the skin.

What Causes Toenail Fungus?

A fungal infection usually develops when a fungus enters the toenail via a crack, cut, or bruise on the toenail or the skin near it. There are various factors that can result in toenail fungus.

We’ve listed some of the common and rare causes below.

Common Causes

Physical trauma

Blunt force to the nail can cause blood to pool under the nail, which breaks the seal between the nail and its bed. This provides a point of access for fungus to enter the nail.

Certain environments

Public places and environments that are warm and wet can expose you to fungal infections, especially if you are walking around these places barefoot. Think of a public swimming pool, showers, or a gym locker room. Wearing non-breathable shoes in which sweaty feet are kept warm and moist, provides the perfect breeding ground for a fungal infection to take root and spread.

Boots and sweaty socks that are tight, warm, and provide little room for your toes to move comfortably, are likely to cause fungal infections, too.

Toenail Fungus Risk Factors

As you age, you become more susceptible to toenail fungus. The Journal of Clinical Pharmacy and Therapeutics states that up to 50% of people over the age of 70 are affected by onychomycosis.

This is usually due to their weakened immune systems and poor circulation, slower nail growth, difficulty in maintaining foot hygiene, and more frequent nail injuries.

Other factors that increase your chances of contracting toenail fungus include:

• Athlete’s foot (tinea pedis): A form of fungus that causes one’s foot to itch, sting, or burn.
• Hyperhidrosis: A disorder in which a person sweats excessively.
• Poor blood circulation: Due to peripheral vascular disease.
• Psoriasis: A skin condition that results in dry itchy patches on the skin.
• Diabetes.
• A weakened immune system: Due to cancer or HIV.
• Venous insufficiency: A condition in which a person’s veins have trouble sending blood back to the heart.
• Peripheral arterial disease: A condition in which your arteries are narrowed and can’t carry as much blood to the arms and legs.

What if It's Not Toenail Fungus?

If you have a black toenail or discolored toenail, it may not be the result of a fungus at all. Let’s take a closer look.

Alopecia areata

This is an autoimmune disease typically associated with hair loss on the scalp. Alopecia can, in fact, also affect other areas of the body such as the nails.

Nails may become pitted, rough, and develop white spots.

Darier Disease

This rare genetic disorder is characterized by yellowish wart-like blemishes on the skin. In some cases, people may also experience red and white streaks on their nails as a result of the disease.

Yellow Nail Syndrome

A rare condition that causes nails to grow slowly, gradually turn yellow, thicken, and sometimes separate from the nail bed. This can result in nail loss.

The exact cause of the syndrome is unknown, but it’s often seen in people with health conditions such as cancer, autoimmune diseases, and lymphedema. Lymphedema happens when your body's lymphatic system is not working as it should.

Melanoma

Although extremely rare, black or brown spots under your toenail could be an aggressive form of skin cancer called melanoma.

Other underlying diseases

Conditions such as diabetes, anemia, and kidney and heart disease can also cause darkened toenails.

Is Toenail Fungus Contagious?

Toenail fungus is contagious and can spread easily between people and from infected surfaces.

For this reason, it’s recommended to never share toenail and foot products such as nail clippers, nail files, shoes, and towels.

The fungus can also spread from the nails to other parts of the body, resulting in fungal skin infections such as athlete’s foot or jock itch (tinea cruris).

Types of Toenail Fungus

Onychomycosis accounts for one-third of fungal skin infections. There are three main types of onychomycosis fungus:

Subungual onychomycosis

This is the most common form of infection and usually results in white, brown, or yellow discoloration of the nail.

The infection starts on the tip or sides of the nail and spreads from there. This is the same fungus that causes athlete's foot and is caused by dermatophytes.

White superficial onychomycosis

This infection begins with white patches on the surface of the nail and spreads to the entire nail over time. It leads to a soft, crumbly, and rough nail texture.

Candida onychomycosis

This is a rare infection caused by yeast.

It affects the fingernails more than the toenails and generally occurs in people who spend a lot of time in the water. The infection usually enters the nail via a cut or bruise of the nail.

How Do I Know if I Have Toenail Fungus?

Because toenail fungus develops slowly, it may go undetected for a while before you start to notice something’s wrong. The initial signs are often very subtle.

Symptoms of toenail fungus

The symptoms of toenail fungus may vary depending on the type of nail fungus and the severity of the infection. Symptoms are initially subtle and gradually get worse over time. They include:

• Discoloration of toenails. Initially, a small area of the toenail will appear discolored and will slowly spread to the rest of the nail.
• Thickened toenails. As the toenails thicken, they become ragged, misshapen, and crumbly in texture.
• Separation of nails from the nail bed.
• Foul odor. The infection typically smells sour or like cheese.
• The big toe is most commonly affected, but over time the infection spreads to other toes.
• The infection usually begins at the side or end of the toenail and spreads toward the cuticle.
• The condition is generally painless unless shoes consistently press down on the nail or the nail bed is damaged.

How is Toenail Fungus Diagnosed?

Proper diagnosis requires taking a sample of nail clippings to send for laboratory testing.

There are a number of other diseases that could result in discolored or black toenails such as:

• Anemia
• Diabetes
• Heart disease
• Kidney disease

This is why a proper diagnosis is vital in determining a treatment path moving forward.

In some cases, patients may have a nail fungal infection as well as another disease that is contributing to the problem.

Medical Treatment Options for Toenail Fungus

Treatment of nail fungus can be tricky and requires a long-term treatment plan for months or even years. Even then, the fungus may return.

This is often the case with people who also have other conditions as well, such as diabetes. The infection will not disappear on its own and if left untreated could lead to a fungal skin condition such as cellulitis, a potentially serious skin infection. For this reason, it’s recommended to see a doctor early if you suspect you may have an infection.

Nails are made out of keratin, which cannot absorb creams and ointments as the skin does. This makes treatment difficult and improvements may take up to a year to be noticeable. Treatment options will vary from person to person depending on the severity of possible drug interactions and effects.

In severe cases, the best option may be the complete removal of the nail which can be done as an out-patient procedure.

Oral antifungal medication

Oral antifungal medications are usually the first line of treatment recommended and are taken for around 12 weeks. These medications include:

• Terbinafine (Lamisil®)
• Itraconazole (Sporanox®)
• Fluconazole (Diflucan®)

Oral antifungal medications have a high success rate but may result in unwanted side effects.

People with heart, liver, or renal disease are discouraged from taking these medications.

Common side effects include nausea, vomiting, headaches, rash, and more. These medications may have negative interactions with other medications and won’t be suitable for everyone.

If you choose to take oral antifungal medication, you will need to take it over a long period of time. Your healthcare provider will use blood tests to monitor your liver function and look into any other unwanted side effects.

Topical medication

Topical medications come in the form of ointments, creams, and sprays, and are most effective when paired with oral medication.

In the U.S., ciclopirox 8% solution is the only topical prescription medication available and approved by the FDA for the treatment of onychomycosis.

Ciclopirox 8% is formulated to be applied as a nail lacquer; it may result in side effects such as burning, itching, and stinging.

If you experience more serious side effects such as blistering, swelling, or oozing from the affected toenail, you should contact your healthcare professional immediately.

Laser treatments

Laser treatment for toenail fungus is a more recent treatment option and generally won’t be prescribed as a patient’s first line of treatment.

A few treatment sessions over a number of weeks will be required; it’s generally a painless process.

In sessions, an infrared laser penetrates the toenail and destroys the fungus. Data is still limited regarding how effective this treatment is.

Over-the-counter treatments

There are a number of OTC treatment options such as:

• Topical mentholated cream (Vicks Vaporub)
• Tea tree oil
• Snakeroot extract (ageratina pichinchensis)

Some research and clinical trials were done to evaluate the effectiveness of these treatments. Their results have shown limited to moderate success, but more data is needed to evaluate the longer-term effectiveness of these options.

At-home remedies for toenail fungus

Home remedies for treating toenail fungus are not as effective and results may be slower.

There are natural products that contain antibacterial properties that may ease some symptoms in the short term, but you may experience recurrent infections over time.

However, should you choose to go this route, here are some options you might want to consider:

• Garlic
• Vinegar
• Listerine mouthwash
• Lavender oil
• Oregano oil
• Ozonized oils such as sunflower oil
• Olive leaf extract

When it comes to treatment options, speak to a podiatrist (foot doctor) or dermatologist to determine which treatment will be best for you.

Can Toenail Fungus Come Back?

Regardless of which treatment methods are used, recurrent infections are fairly common. There are a number of reasons why an infection may reoccur.

It’s important to keep in mind that sometimes treatments may not be effective due to there being more than one cause of the infection. For example, a patient could have toenail fungus as well as psoriasis, a skin condition that results in an itchy rash and dry patches.

Another reason could be that the toe fungus is drug-resistant or is made up of multiple organisms.

Poor foot hygiene, age, genetic factors, and the presence of other diseases are some of the other factors that may result in recurrent infections.

What Happens if Toenail Fungus is Left Untreated?

If left untreated, toenail fungus could lead to other conditions such as:

Cellulitis

Cellulitis is an infection of the deeper skin layers and is caused by bacteria. It commonly affects the arms and legs but can also occur around the mouth, eyes, anus, or belly.

Bacteria generally enter the body through a break in the skin — this can be the result of injury or surgery.

There are studies that suggest a fungal infection may be a factor in the development of cellulitis in the feet.

The infection can potentially be fatal if it spreads to other parts of the body such as the heart or the nervous system. Patients could also end up losing a limb due to gangrene — which is when the body tissue dies.

Athlete’s foot and jock itch

Athlete’s foot and jock itch are both caused by ringworm, which is a type of fungus. This infection is called by different names depending on what part of the body is affected.

In the foot, it’s called athlete's foot and it results in red and itchy feet. Generally, it affects the spaces between toes but can also infect the whole foot or the hands. While it’s not serious, it can be difficult to treat.

When the ringworm fungus affects the groin, anus, or inner thigh it is called jock itch. Jock itch is a mild infection in which the skin becomes cracked, scaly, and red.

With both athlete's foot and jock itch, practicing good hygiene is key to prevention. Keep your body clean and dry, and avoid tight-fitting clothes that trap moisture.

Loss of the entire nail

If the infection is severe, removing the entire nail may be the best option. This is why it’s important to catch an infection early.

Pain or discomfort

As toenails become more misshapen, it may become painful to walk and wear shoes. This highlights the importance of keeping toenails straight through proper grooming.

How Can I Prevent Toenail Fungus?

There are a number of steps you can take to prevent toenail fungus. We’ve listed some preventative measures below:

• Practice good foot hygiene. This includes keeping your feet clean and dry and your toenails short.
• Wear shoes in public places such as showers or gyms.
• Wear socks that absorb excess moisture. Acrylic socks are better than cotton for this reason.
• Don’t share nail clippers with anyone.
• Choose a salon that is clean and hygienic and where all equipment is properly sterilized. Salons that adhere to regular and thorough hygiene practices should be safe to visit.
• Wear comfortable, breathable shoes and absorbent socks.
• Disinfect and clean shoes regularly.
• Frequently use antifungal products on toenails to limit one’s risk of contracting a fungus.
• Wear properly fitted shoes. Avoid shoes that are tight, non-breathable, and squeeze your toes.

Where Can I Learn More About Toenail Fungus?

If you’re currently experiencing some of the symptoms mentioned here or are concerned about a potential infection, you can speak to a board-certified doctor or nurse practitioner right from home. Head over to LifeMD to make a video appointment.