Superficial Fungal Infections (Skin, Nail, Hair, Mucous Membranes)
Superficial fungal infections may be caused by both yeast and mold forms of fungi. Skin is normally populated with a mixture of microbes called normal flora. Most of the time, normal flora do not cause illness and do not stimulate the immune system. If there is a break in the skin or if the immune system becomes weakened, then any of the microbes present can cause a wound or skin infection. If there is a shift in the balance of the microbes, such as a decrease in bacteria and an increase in the growth of fungi (sometimes seen with the use of broad-spectrum antibiotics), then the person may experience a fungal infection associated with the imbalance.
Candidiasis is a common yeast infection that is due primarily to the overgrowth of Candida albicans and other species of Candida, which are part of the normal flora. In the mouth, candidiasis causes redness and white patches and is called "thrush." In babies, candida infections can cause diaper rash. In women, they can cause genital itching and vaginal discharge that is referred to as a "yeast infection." According to the Centers for Disease Control and Prevention (CDC), almost 75% of women will have at least one yeast infection in their lifetime. Men can also get genital yeast infections, although this is rare. Candidiasis can cause a variety of other infections, including nail infections, and it can become systemic, especially in those who have a weakened immune system. (Read about Systemic Infections).
Athlete's foot, jock itch, and fungal nail infections are common infections that can be passed from person to person. These fungal infections can cause reddening, peeling, blistering, and scaling of the skin; itching, deformation and brittleness of affected nails; and brittle hair. They are caused by dermatophytes, a group of fungi that includes Trichophyton, Microsporum, and Epidermophyton species. Dermatophytes feed on keratin and rarely penetrate below the skin. Infections caused by these fungi are also commonly called ringworm (although they are not caused by a worm) and "tinea."
- Athlete's foot (tinea pedis) is found between the toes and sometimes covers the bottom of the foot.
- Jock itch (tinea cruris) may extend from the groin to the inner thigh.
- Scalp and hair infection (tinea capitis) affects hair shaft, primarily in children.
- Finger or toenail infection (tinea unguium) typically affects toenails but may also affect fingernails.
- Ringworm of the body (tinea corporis) can be found anywhere on the body.
- Barber's itch (tinea barbae) affects the bearded portion of the face.
Tinea versicolor is associated with multicolored patches or lesions on the skin and is caused not by a dermatophyte, but by Malassezia furfur, a yeast. It is a condition that is common in young adults. Sporotrichosis is a condition caused by the fungus Sporothrix schenckii, which is not a dermatophyte. It is an infection of the skin and subcutaneous tissue that has been abraided by thorny plants, pine needles, and sphagnum moss where this fungus normally resides. Some fungi associated with systemic infections, such as Coccidioides immitis and Blastomyces dermatitidis, may also cause skin rashes or lesions.