February 10, 2007

Fungal Skin Infections


Fungi usually make their homes in moist areas of the body where skin surfaces meet: between the toes, in the genital area, and under the breasts. Many fungi that infect the skin (dermatophytes) live only in the topmost layer of the epidermis (stratum corneum) and do not penetrate deeper. Obese people are more likely to get these infections because they have excessive skinfolds. People with diabetes tend to be more susceptible to fungal infections as well.

Strangely, fungal infections on one part of the body can cause rashes on other parts of the body that are not infected. For example, a fungal infection on the foot may cause an itchy, bumpy rash on the fingers. These eruptions (dermatophytids, or id reactions) are allergic reactions to the fungus. They do not result from touching the infected area.

A doctor may suspect a fungal infection upon seeing a red, irritated, or scaly rash in one of the commonly affected areas. The doctor can usually confirm the diagnosis by scraping off a small amount of skin and having it examined under a microscope or placed in a culture medium that will grow the specific fungus so that it can be identified (see Diagnosis and Treatment of Skin Disorders: Diagnosis).

Candidiasis (yeast infection, moniliasis) is infection by the yeast Candida, formerly called Monilia.

Candida is a normal resident of the mouth, digestive tract, and vagina that usually causes no harm. Under certain conditions, however, Candida can infect mucous membranes and moist areas of the skin. Typical areas of infection are the lining of the mouth and vagina, the genital area and anus, the armpits, the skin under the breasts in women, and the skinfolds of the stomach. Conditions that enable Candida to infect the skin include hot, humid weather; tight, synthetic underclothing; poor hygiene; and inflammatory diseases, such as psoriasis, occurring in the skinfolds.

People taking antibiotics may develop candidiasis because the antibiotics kill the bacteria that normally reside on the body, allowing Candida to grow unchecked. Corticosteroids or immunosuppressive therapy after organ transplantation can also lower the body's defenses against candidiasis. Inhaled corticosteroids, often used by people with asthma, sometimes produce candidiasis of the mouth. Pregnant women, obese people, and people with diabetes also are more likely to be infected by Candida.

In some people (usually people with a weakened immune system), Candida invades deeper tissues as well as the blood, causing life-threatening systemic candidiasis


Symptoms vary, depending on the location of the infection.

Infections in skinfolds (intertriginous infections) or in the navel usually cause a bright red rash, sometimes with softening and breakdown of skin. Small pustules may appear, especially at the edges of the rash, and the rash may itch intensely or burn. A Candida rash around the anus may be raw, white or red, and itchy. Babies may develop a Candida rash in the diaper area (see Problems in Infants and Very Young Children: Rashes).

Vaginal candidiasis (vulvovaginitis, yeast infection (see Vaginal Infections) is common, especially in women who are pregnant, have diabetes, or are taking antibiotics. Symptoms of these infections include a white or yellow cheeselike discharge from the vagina and burning, itching, and redness along the walls and external area of the vagina.

Penile candidiasis most often affects men with diabetes, uncircumcised men, or men whose female sex partners have vaginal candidiasis. Usually the infection produces a red, raw, sometimes painful rash on the head of the penis and sometimes the scrotum. Sometimes the rash may not cause any symptoms.

Thrush is candidiasis inside the mouth (see Periodontal Diseases: Gingivitis due to Infections). The creamy white patches typical of thrush cling to the tongue and sides of the mouth and may be painful. The patches cannot be scraped off easily with a finger or blunt object. Thrush in otherwise healthy children is not unusual, but in adults it may signal a weakened immune system, possibly caused by diabetes or AIDS. The use of antibiotics that kill off competing bacteria increases the chances of getting thrush.

Perlèche is candidiasis at the corners of the mouth, creating cracks and tiny cuts. It may stem from chronic lip licking, thumb sucking, ill-fitting dentures, or any other condition that leaves the corners of the mouth moist enough so that yeast can grow.

Candidal paronychia is candidiasis in the nail beds, producing painful redness and swelling (see Foot Problems: Onychomycosis). Nails infected with Candida may turn white or yellow and separate from the nail bed. This disorder typically occurs in people with diabetes or a weakened immune system or in otherwise healthy people whose hands are subjected to frequent wetting or washing.

Diagnosis and Treatment

Usually, a doctor can identify candidiasis by observing its distinctive rash or the thick, white, pasty residue it generates. To confirm the diagnosis, a doctor may scrape off some of the skin or residue with a scalpel or tongue depressor. The sample is then examined under a microscope or placed in a culture medium (a substance that allows microorganisms to grow) to identify the specific fungus.

Generally, candidiasis of the skin is easily cured with creams containing miconazole
, clotrimazole, oxiconazole, ketoconazole, econazole, ciclopirox, or nystatin . The cream is usually applied twice daily for 7 to 10 days. Corticosteroid creams are sometimes used along with antifungal creams because they quickly reduce itching and pain (although they do not help cure the infection itself). Candidiasis that does not respond to antifungal creams and liquids may be treated with gentian violet, a purple dye that is painted on the infected area to kill the yeast.

Keeping the skin dry helps clear up the infection and prevents it from returning. Talcum powder helps keep the surface area dry, and talcum powder with nystatin may further help prevent a recurrence.

Different treatments are prescribed for vaginal yeast infections, thrush, and nail infections.

Adapted from: Merck & Co., Inc