What Are Athlete’s Foot (Tinea Pedis) &
Nail Fungus (Tinea Unguium)?

Tinea pedis, commonly known as athlete’s foot, is an infection of the skin of the feet by a fungus (mold) called a dermatophyte (tinea). Blisters and peeling appear between the toes and on the soles, and it may or may not be itchy. When the fungus infects the nails, it is called tinea unguium (nail fungus). It most often affects the toenails, but can also occur on the fingernails.

Because the dermatophyte fungus feeds on a protein called keratin, it lives in the keratin layer of the skin and in the nails. It prefers hot, humid environments and is abundant in places where people walk barefoot, such as hot springs and swimming pools. In Japan it tends to spread or worsen during the humid rainy season, and it troubles a great many people. Those who sweat easily or wear leather shoes for long periods are especially prone to it, and people with diabetes need to be careful, as they are at higher risk of a complicating bacterial infection.

Athlete’s Foot (Tinea Pedis)

Athlete’s foot is divided into the following three types.

Interdigital type (between the toes)

“Interdigital” refers to the spaces between the toes.
It is characterized by redness and blisters, with the skin turning white and soggy or becoming raw and inflamed.
It is often itchy, and if the raw skin develops a bacterial infection, pain appears and the redness spreads.
It is especially likely to develop in the fourth space between the toes (between the fourth toe and the little toe).

Vesicular type (small blisters)

Small blisters form on the soles and sides of the feet, accompanied by intense itching. When the blisters break, the skin peels and there may be pain or a stinging sensation. This type tends to appear during the rainy season; even if left untreated it often improves somewhat by autumn, then reappears as the humidity rises again.

Hyperkeratotic type (thickened skin)

The keratin layer thickens mainly on the soles and heels, making the surface rough and hard. Itching is mild, but cracks can develop that are painful. Topical medications are less effective and oral medications work better, though their side effects require attention.

Nail Fungus (Tinea Unguium)

When the dermatophyte fungus infects the nails, it is called tinea unguium. It usually affects the toenails, but occasionally the fingernails. Tinea unguium is divided into the following four types.

1. Distal lateral subungual onychomycosis

A type in which the nail becomes cloudy and thickened starting from the tip or the sides.

2. Superficial white onychomycosis

A type in which only the surface of the nail becomes cloudy.

3. Proximal subungual onychomycosis

A type in which the cloudiness begins from the base of the nail.

4. Total dystrophic onychomycosis

A type in which the entire nail becomes cloudy, thickened, and brittle.

How to Prevent Athlete’s Foot & Nail Fungus

Keep your feet clean

Even when the fungus lands on the skin, it takes time for it to penetrate the keratin layer. It is important to wash your feet carefully every day, including between the toes. After washing, dry them thoroughly with a towel; keeping them dry makes infection less likely. People who sweat easily on their feet, or who are in hot, humid environments, should wash frequently.

Choose breathable shoes and socks

Poorly ventilated shoes and synthetic socks make the feet sweaty and create conditions in which the fungus thrives. Choose highly absorbent cotton or linen socks, and to keep moisture from building up inside your shoes, avoid wearing the same pair every day by rotating among several pairs, or place a desiccant inside them.

Do not share items that touch the skin

The fungus can be transmitted via slippers, towels, bath mats, and the like. If someone in your household has athlete’s foot, it is important to avoid sharing these items and to use your own.

Precautions when using public facilities

Places where people walk barefoot, such as hot springs, pools, and gym changing rooms, harbor a lot of the fungus. Wearing sandals inside such facilities, washing and thoroughly drying your feet after use, and heading straight to the bathroom to wash your feet when you get home all help keep you from bringing the fungus into your house.

Testing for Athlete’s Foot & Nail Fungus

We take a sample of keratin or a piece of nail from the affected area and check directly under a microscope for the presence of the fungus. For nails, when nothing is found under the microscope, an antigen test may also be performed. Because it is difficult to distinguish from eczema or a nail deformity on your own, receiving a proper diagnosis is important.

Treatment of Athlete’s Foot & Nail Fungus

Below, only the original brand-name drugs are listed for medications.

1. Topical medications (creams and ointments)

For athlete’s foot, topical medications such as Lulicon® ointment/cream/solution, Lamisil® ointment/cream, Pekiron® cream, and Astat® ointment are used. You need to apply them to the entire sole and all of the spaces between the toes. If you run your finger from the top of the foot toward the sole, you will notice the texture change partway: this is because the keratin is thicker on the sole. Use that thicker keratin area as a guide for where to apply. Even after symptoms improve, the fungus may remain, so it is important to come in for regular check-ups and to keep applying the medication for the period you are instructed. For nail fungus, a liquid medication made specifically for the nails is used. There are two types: Clenafin® topical solution and Luconac® nail topical solution. Filing down the thickened, discolored parts to make the nail thinner and shorter helps the medication work better. If you cannot file them yourself, we can do it at our clinic, but if you also care for them at home, for example by filing them with an emery board, with the aim of keeping them from thickening or growing long, the medication will work better. Ointments, creams, and solutions alike can cause irritation in some cases. If irritation occurs, see us promptly and receive treatment for it.

2. Oral medications

For the hyperkeratotic type of athlete’s foot and for nail fungus, an oral antifungal medication may be used. The treatment lasts several months, and because liver function can deteriorate as a side effect, we monitor your progress carefully with blood tests. It may not be possible to take it because of interactions with other medications you are on. It also cannot be taken during pregnancy or breastfeeding. We can also notify you of your results through our app.