Skin Fungus: Information and Doctors Specializing in Skin Fungus

Skin fungi cause infections of the skin, hair, and nails. They derive their nourishment from keratin, which is a major component of the outer layer of the skin, hair, and nails. The inflammation results from the immune system’s defensive response to the foreign organism. 

Most fungi are unable to penetrate deeper into an immunocompetent host. Therefore, dermatomycosis is usually limited to the non-living part of the outer skin layer (epidermis).

The host’s reaction to the foreign organism can range from mild to severe. The course of the inflammation depends on the individual 

• on the specific skin fungus and
• the immune system’s response, or
• the success of medical treatment.

Some of the infections caused by skin fungi are also known as ringworm or tinea.

One in three Germans has to deal with a skin fungus from time to time. Athlete’s foot is by far the most common form and is therefore also one of the most common skin diseases. Athlete’s foot is transmitted from person to person or from an animal.

The risk of dermatomycosis increases with poor hygiene.

Dermatophytes are various types of filamentous fungi. They generally cause only skin infections. These skin infections are then called dermatophytoses (or, more generally, dermatomycoses).

The prefix “dermato-” refers to the “dermis,” or skin. This root is also found in the technical term for skin doctors (dermatologists). The suffix “-phyte” can also refer to plants in scientific contexts. In microbiology, however, it is most commonly used to refer to dermatophyte species.

A mycosis, meanwhile, is always a parasitic fungal infection of living tissue. Depending on the location of the fungal infection, the terms used are

• tinea pedis (athlete’s foot),
• tinea unguium (nail fungus),
• tinea capitis (on the scalp),
• tinea inguinalis (jock itch),
• tinea barbae (fungal infection of the beard), and
• Tinea corporis (the rest of the body).

The causative agents of skin fungal infections are mostly dermatophytes. These fungi almost exclusively infect keratinized areas of the body such as the skin, nails, or hair.

Microbiology distinguishes three relevant genera of dermatophytes:

• Trichophyton,
• Microsporum, and
• Epidermophyton.

A further classification into

• geophilic,
• zoophilic, and
• anthropophilic dermatophytes

takes into account, among other things,

• the habitat,
• the pathogen reservoir, and
• the various chains of transmission.

Geophilic dermatophytes live in the soil. Contamination can occur, for example, during gardening, though this does not inevitably lead to infection. Only local predisposing factors, such as

• circulatory disorders (“cold feet”),
• mechanical stress from shoes that are too tight, or
• moisture (sweating)

that make it easier for the ubiquitous pathogen to initiate an infection.

Zoophilic dermatophytes live primarily on the fur of animals. They are transmitted through contact (e.g., a child cuddling a guinea pig). One example in rural areas is Trichophyton verrucosum, which causes “cattle ringworm” in animals. Under favorable conditions, the fungus can also be transmitted to humans. Zoophilic dermatophytes can cause more severe infections in humans.

Anthropophilic dermatophytes are adapted to humans. They can be transmitted from person to person, either directly or via contaminated objects. They are highly infectious but tend to cause only mild symptoms. The two “prime suspects” in this group are

• Trichophyton rubrum (primarily affects the skin) and
• Trichophyton mentagrophytes (primarily affects hair).

Up to 90 percent of all fungal skin infections are caused by these two pathogens.

Dermatophytes thrive wherever it is moist, warm, and dark. That is why they particularly like to infect

• the feet, particularly the spaces between the toes and
• skin folds, such as under the female breast, in the armpit, or in the groin.

As a result, “athlete’s foot” is a very common condition. Athletes with sweaty feet in warm, tight shoes provide ideal growing conditions for dermatophytes.

In addition, athletes frequently use communal showers and spend time in locker rooms. The pathogen is transmitted either

• directly from skin to skin or
• via the floors of gyms, showers, saunas, etc.

The filamentous fungus Trichophyton tonsurans likely migrated to this country from the United States. It is often found in gymnasts and wrestlers—it is also known as the “gym mat fungus.”

Otherwise, there are predisposing factors for any type of fungal skin infection:

• Diabetes mellitus weakens the immune system, thereby increasing susceptibility to fungal skin infections.
• Peripheral arterial disease (PAD, “intermittent claudication”) leads to poor circulation in the hands and feet. This makes it easier for pathogens to take hold.

Microsporum canis is being transmitted with increasing frequency. Cats are the primary reservoir for this pathogen. Young children are most commonly affected. The fungus takes advantage of their immune systems, which are not yet fully developed. It primarily affects the hair (tinea capitis).

Healthy skin can generally prevent harmful organisms from penetrating it. The outermost layer of the skin consists of flat, dead cells. These dead cells form a protective layer over the other layers of the skin.

Above this layer, the skin has an acid mantle formed by sebum and sweat. This acid mantle creates a very hostile environment for many bacteria, viruses, and fungi. If the acid mantle or the skin layer becomes permeable, the skin becomes susceptible to invaders.

The most common fungal skin infections are:

Ringworm (Tinea corporis)

Ringworm, or tinea corporis, is a fungal skin infection that affects

• legs,
• arms,
• upper body, or
• face

. They cause itchy, ring-shaped rashes.

Athlete’s foot (tinea pedis)

Tinea pedis is a specific type of fungal infection of the feet. This form of the infection affects more men than women. The infection usually begins between the toes. Moisture tends to accumulate there, making the area particularly susceptible to infection.

The fungal infection can then spread across the sole of the foot.

Tinea cruris

Tinea cruris also affects the foot. The pathogens enter the body through a break in the skin’s surface after coming into contact with contaminated ground.

Tinea capitis

Tinea capitis is a specific form of fungal skin infection. It affects the hair follicles and manifests as black dots on the scalp.

Fungal infections are usually characterized by severe itching. They may also cause

• redness,
• peeling skin,
• cracks, or
• ring-shaped rashes

may also occur. If the fungal infection affects the scalp or beard, it can lead to hair loss.

Infected nails become thick, discolored, and may also become deformed. Very serious infections can lead to abscesses or cellulitis.

The diagnostic process begins with a medical history interview. During this interview, the doctor asks

• the location of the infection,
• your place of residence,
• past travel destinations, or
• contact with animals.

Ethnic background may also play a role.

Hyphen-forming fungi can often be identified directly, as they leave a thread-like structure in the outermost layer of the skin.

Trichophyton is the fungus that causes tinea capitis. It can be identified by small, dark crusts at the hair roots.

For a complete identification of the skin fungus, a sample must be observed on a culture medium. Fungal growth begins after 5 to 14 days. A laboratory analysis of this medium is the most accurate method for identifying the skin fungus.

A special rapid test has been developed for the most common skin fungi. This test involves swabbing the infected skin area. A bacterial culture medium is integrated into the test. At a constant room temperature, the skin fungus grows in the test and changes color accordingly. This eliminates the need for further analysis under a microscope.

The primary goal of treating a dermatomycosis is to eliminate the fungus from the affected areas. Infections are treated based on their presentation.

Whether treatment is systemic or topical also depends on the type of skin fungus.

The first steps involve educating the patient about skin fungus. This includes

• changing footwear,
• using powders to keep the feet dry,
• avoiding walking barefoot in public places, and
• advising the patient not to share clothing, towels, combs, and other personal items with others.

Treatment of Tinea Capitis

The systematic use of antifungal medications is the mainstay of treatment for fungal infections. The duration of treatment depends on the choice of medication and can range from 2 to 8 weeks. Safety, cost, and efficacy depend on the choice of medication.

Griseofulvin is the oldest oral medication. More recent medications include terbinafine and itraconazole. All three are highly effective, first-class medications, especially for use over shorter periods of time.

Studies have shown that terbinafine is more effective in treating tinea capitis caused by Trichophyton strains. The opposite is true for Microsporum strains.

Studies have been conducted on both ketoconazole and fluconazole for tinea capitis. Both drugs have proven to be effective. Thus, they are good alternatives if

• the patient is intolerant to griseofulvin, terbinafine, and itraconazole, or
• cost considerations are a factor.

Ketoconazole and fluconazole are used only as second-line treatments. They carry a higher risk of side effects. Antifungal shampoos generally do not resolve the infection itself. However, they are a good solution for stopping the spread of the fungus.

Treatment of Tinea faciei, Tinea corporis, Tinea cruris, or Tinea pedis

These types of fungal skin infections are usually found in the outermost layer of the skin. They therefore respond to topical treatment. Research has not yet been able to demonstrate significant differences in the effectiveness of the various topical antifungal medications. However, the allylamine class of medications appears to be preferable for topical treatment.

Tinea pedis (athlete’s foot) is usually difficult to eliminate. Athlete’s foot can spread rapidly if a reservoir of infection

• in the nail bed or
• in the thick layer of skin on the sole of the foot

. Regular disinfection of shoes or even replacing them may be necessary. If the fungal infection also affects the soles of the feet, a topical antifungal spray can help. It should be applied over the entire surface of the foot. The thick layer of skin on the sole of the foot, in particular, is an ideal breeding ground for fungi. Therefore, long-term treatment may be necessary. This is a common problem for people with weakened immune systems.

If treatment fails, it is often due

• due to the patient not following the treatment correctly,
• a misdiagnosis, or
• a lack of knowledge about the patient’s immune deficiency.

Personal Hygiene

Once a fungal infection has taken hold in the skin, treatment can be lengthy and unpleasant.

The main causes of fungal infections are poor hygiene. Therefore, skin fungal infections can be effectively prevented.

This includes drying off thoroughly after washing or bathing. Pay special attention to body creases such as the armpits, the backs of the knees, and between the toes. Moisture accumulates quickly in these areas, making them ideal breeding grounds for fungi.

Always use your own towel for this purpose and do not share it with anyone.

Clothing

Clothing worn directly against the skin should be washed regularly at a temperature of at least 60 degrees. Higher temperatures effectively destroy skin fungi.

Underwear and socks, in particular, must be changed every day.

Problem Area: Feet

Places like public bathhouses or showers are hotspots for skin fungi. Be sure to always wear shower shoes and avoid walking barefoot. This also applies to inns or hotels. It’s best not to walk on the floor there without shoes.

Choosing the right footwear is another important factor. Use trial socks when trying on shoes. This helps protect you from any fungal pathogens left behind by previous customers.

Do you tend to have sweaty feet? Then switch from heavy winter boots to lighter shoes as soon as possible in the spring. The longer your feet are in a damp and stuffy environment, the faster a fungal infection will develop. It’s a good habit to thoroughly clean and dry your feet before going to bed.

Since the risk of infection with athlete’s foot is very high, caution should be exercised when coming into contact with infected individuals. However, disinfecting (with spray) your own clothing after contact should be sufficient.