All about cutaneous mycoses.

Recognizing a fungal infection of the skin is based primarily on observing visible changes in the epidermis, which are often accompanied by unpleasant physical sensations. The most universal sign is itching, sometimes so intense that it leads to scratch-induced skin lesions. Visually, the infection often appears as redness or localized inflammation, but the exact appearance depends on the group of fungi involved. For example, ringworm of the body, which has nothing to do with the herpes virus, forms a round red patch with a more pronounced border and a center that seems to be healing, while “athlete’s foot” presents as peeling skin that turns white and eventually cracks between the toes.

The infection can also alter the texture of the skin, leading to peeling or the appearance of small fluid-filled blisters. In skin folds, such as the armpits, under the breasts, or in the groin area, the fungal infection often appears as a bright red, moist, and sometimes shiny patch, often bordered by small pustules: this is the classic sign of intertriginous candidiasis (yeast infection of the skin folds). Finally, on the scalp, the fungal infection can cause “patches” of hair loss where the hairs break off at the root. This condition is known as ringworm of the scalp (tinea capitis).

If you notice a spot that is gradually spreading, itchy, and shows raised edges or flaking of the skin, a fungal cause should be strongly suspected.

The development of a cutaneous fungal infection results from an imbalance of the microbiome.

The infection process generally begins when microscopic spores are deposited on the epidermis, often via infected skin flakes left by another person on a damp floor. If the skin barrier is healthy and dry, these spores are naturally removed through normal cell renewal. However, if they encounter a favorable environment, they germinate and produce filaments called hyphae. These filaments insinuate themselves between the cells of the stratum corneum and secrete enzymes to digest the tissues, thereby triggering the body’s inflammatory response, which appears as redness and itching. Three major families of fungi are primarily identified as responsible for skin mycoses:

• Dermatophytes : These fungi are keratinophilic, meaning they feed almost exclusively on keratin. They never penetrate into deep tissues but instead spread outward in a circular pattern on the surface.

• Yeasts, of the Candida type: Naturally present in our mucous membranes, they become pathogenic when the microbiota is imbalanced. They particularly favor skin fold areas where moisture is constant.

• The Malassezia : This lipophilic yeast feeds on the fats produced by our sebaceous glands. It is responsible for characteristic pigmented spots on the chest or back.

The underlying cause of the proliferation of these fungi is almost always linked to the phenomenon of maceration.

The combination of body heat and moisture, for example related to sweat or incomplete drying after a shower, creates an ideal culture medium, because it softens the skin’s protective barrier and facilitates fungal invasion. This is why shared environments such as swimming pools, saunas, or locker rooms in gyms are major sites of contamination: stagnant water on porous floors keeps fungi alive for several hours, waiting for a barefoot person to pick them up.

Beyond environmental factors, certain internal conditions promote the development of a fungal infection. A recent course of antibiotics, by eliminating the beneficial bacteria that regulate the population of fungi on our skin, gives these fungi free rein to colonize the available space. Similarly, a temporarily weakened immune system or conditions such as diabetes, which increase sugar levels in tissues—an ideal nutrient source for yeasts—facilitate the establishment of infections. Finally, the use of overly harsh hygiene products alters the natural pH of the skin, destroying the protective acid mantle and making the epidermis much more permeable to external irritants.

The treatment of a cutaneous fungal infection relies primarily on the use of antifungal agents, whose role is to destroy the fungus and prevent it from multiplying.

In the vast majority of cases, local treatment is more than sufficient. It comes in the form of creams, gels, sprays, or powders applied directly to the infected area. Depending on the type of fungus, the doctor or pharmacist may prescribe imidazole derivatives or ciclopirox olamine. The most critical factor for successful treatment is its duration: it is essential to continue applying it for the entire prescribed period, often about four weeks, even if visible signs disappear after a few days. Microscopic spores can survive on the surface and cause an immediate relapse if the treatment is stopped too early.

In more complex situations, such as widespread fungal infections, scalp ringworm, or infections that do not respond to creams, treatment by the oral route may be necessary. These tablets allow the antifungal agent to circulate in the bloodstream and reach the deeper layers of the skin, hair, or nails from the inside. This type of treatment always requires a medical prescription and monitoring, because it may involve contraindications or drug interactions. In addition to medications, the use of specific soaps with a neutral or slightly alkaline pH may be recommended to soothe inflammation and limit the proliferation of yeast such as Candida, which thrive in acidic environments.

The effectiveness of medical treatment is inseparable from strict hygiene measures to break the cycle of contamination. In particular, it is important to keep the infected area completely dry. After showering, gently pat the skin with a clean towel without rubbing, or use a hair dryer for hard-to-reach areas, such as skin folds or the spaces between the toes. To avoid reinfecting yourself, wash your towels, sheets, and socks at a high temperature (at least 140°F / 60°C) and do not share your personal items. Finally, for athlete’s foot and other fungal infections of the feet, using antifungal powders in your shoes can help destroy the spores that are present there and thereby prevent any new infectious episode.

• LORTHOLARY Fungal skin and soft tissue infections. Current Opinion in Infectious Diseases (2016).

• WELSH O. & al. Cutaneous mucormycosis. Anais Brasileiros de Dermatologia (2017).

• PETRIKKOS G. & al. Global cutaneous mucormycosis: A systematic review. Journal of Fungi (2022).

• OSMANCEVIC A. & al. Diagnostic outcomes and treatment modalities in patients with mycosis fungoides in West Sweden—A retrospective register-based study. Cancers (2022).

• EKENG B. E. & al. Cutaneous manifestations of deep mycoses in Nigeria: A systematic review. Therapeutic Advances in Infectious Disease (2024).