What is a fungal infection?
Of the many thousands of species of fungi that exist, a few live in and on the skin. Among these fungi there are also “specialists” that prefer certain parts of the skin. Two of the most common fungal skin infections are athlete’s foot and fungal nail, which are covered in separate articles.
Which types of fungal skin infection are there?
“Ordinary” fungal infection of the skin (tinea corporis)
All fungal skin infections fall into this group, except those of the palms, soles, toes and groin. In many cases these infections have a characteristic scaly ring shape and are therefore also called ringworm. The main complaint is considerable itch. The most important cause of ringworm is the fungus Trichophyton rubrum. A fungal infection often spreads in a ring shape.
“Deep” fungal infection of the skin (deep mycosis)
Sometimes fungal infections can lead to red, painful bumps and inflammation of the skin. These infections are less common than ringworm and usually involve infections of the hair follicles. The causes include T. mentagrophytes, T. violaceum and Microsporum canis.
Fungal infection of the groin
Fungal infections in the groin are fairly common. Typical is a red, slightly scaly area of skin spreading out from the groin, bordered from the normal skin by a clear, often bright-red edge. The causes are usually Epidermophyton floccosum, T. rubrum or T. mentagrophytes. Fungal infection of the groin is much more common in men than in women.
How do I catch a fungus?
Fungi spread by producing spores. These are very small and occur everywhere around us. The spores that cause the most common skin fungi are found mainly in gyms, swimming pools and other public spaces. Some species, such as M. canis, are often transmitted by pets. The spores can grow into actual fungi when conditions are favourable — usually a warm, moist environment (feet, groin) or a warm climate.
How is the infection diagnosed?
With a very typical picture, the doctor usually needs no further tests and can make the diagnosis by eye. In case of doubt, two kinds of test can be done: direct microscopic examination, in which fungal threads in the skin scales can be detected (the doctor can do this during the consultation); and a fungal culture, in which skin scales are sent to the laboratory and grown on a culture medium — after a few weeks it is known whether there is a fungal infection, and the species can also be determined (many laboratories can now identify fungus with the modern, fast PCR method). For deep infections, a piece of tissue (skin biopsy) may sometimes be needed for examination.
How is a fungal skin infection treated?
Fungi are treated with an antifungal medicine (antimycotic). These can be applied topically or given as an oral course, depending on the type of infection.
Topical treatment. Most fungal skin infections can be treated by applying an antifungal cream, such as clotrimazole, miconazole, terbinafine, ciclopirox or sulconazole. These creams usually need to be applied twice a day for 3–4 weeks.
Oral treatment. When the infection is very extensive or there is a deep infection of, for example, the hair follicles, it is usually necessary to treat with tablets. The drawback is that oral treatment carries more possible side effects than topical treatment, and infections with certain fungal species can need fairly prolonged treatment. Oral antifungals include terbinafine and itraconazole.
When to see a doctor
See a doctor if an itchy, scaly, spreading or ring-shaped rash does not clear with an over-the-counter antifungal cream, if it is widespread or deep, or if you have reduced immunity or diabetes.