The Facts

There are two major causes of fungal infections of the skin and nails: yeast and dermatophytes.

Yeast infections of the skin and nails are generally caused by an organism called Candida albicans. This organism normally makes a quiet home for itself on your skin and doesn't bother anyone. We all carry this organism on our skin (and in other places such as our mouth, our gastrointestinal tract (gut), and the vagina).

Occasionally Candida albicans multiplies uncontrollably, causing a yeast infection (also known as candidiasis). Yeast infections of the skin can cause a red, itchy rash that may leak fluid. Yeast nail infections can lead to pain and swelling, and may cause the nail to separate from the finger or toe.

Dermatophytes are fungi that only live in dead tissue, such as your nails and dead skin cells. Dermatophyte infections can also be called tinea. Dermatophyte infections of the skin can cause a round, scaly rash that may also have blisters. When dermatophytes infect the nails, the nails become thick, split, become dull, and may fall off.

Fungal skin infections may also be caused by a fungus called Malassezia. These infections, also called tinea versicolor, lead to scaly patches that vary in colour from white to brown.

Fungal infections may also affect the skin of the feet. This is also known as athlete's foot. For detailed information this condition, see the article on athlete's foot on this website.

Fungal infections may also affect the vagina. This is also known as vaginitis or female yeast infection. For detailed information this condition, see the article on vaginitis on this website.

Causes

You don't catch yeast infections. The yeast is already there. A number of factors can increase the chance of the yeast growing out of control:

• Overuse of antibiotics. Yeast must compete for the right to live on us with various other species, many of them bacteria. These bacteria, which live on the skin and in the intestine and vagina, among other places, are harmless but good at fighting off yeast. When we take antibiotics to deal with less friendly bacteria, we kill off these harmless ones as well. Yeast, which is unaffected by antibiotics, moves into the vacated spots once occupied by bacteria, and starts to grow and multiply.
• Steroids and some cancer medications weaken the immune system and can allow yeast to flourish.
• Warm, humid environments allow yeast to thrive and overgrow.
• Obesity, diabetes, and pregnancy also encourage yeast infections. Yeast generally infects intertriginous areas (areas where skin contacts skin). Overweight people have more folds in their skin. They also sweat more, and candida albicans is fond of moist skin. Moist diapers can also provide a good environment for the yeast to grow. People with diabetes have high blood glucose and increased glucose levels in other body secretions, which encourages the growth of yeast. Pregnancy causes temporary weight gain and may temporarily weaken the immune system.
• Having your hands in the water frequently or having a poorly done manicure can increase the risk of yeast nail infections.

Dermatophyte infections are potentially contagious. You usually catch them through direct contact with another person or with an animal. You can also catch them through soil contact or contact with objects that an infected person has touched, although this is less common.

Symptoms and Complications

A yeast infection of the skin appears as a clearly defined patch of red, itchy skin. Sometimes this rash can leak fluid. Often small red bumps, or pustules, are also present around the edge of the rash. Scabs may appear there as well. The yeast infection will usually be found in areas such as the groin; the folds of the buttocks; between the breasts, toes, or fingers; in the diaper area; and in the navel. Yeast infections of the skin of the penis are rare but may cause the tip to be red, swollen, and painful.

A yeast infection of the nails, also called Candidal paronychia, can cause a painful red swelling of the affected area that may leak fluid later. In worse cases, the fingernail may separate, showing a discoloured white or yellow nail bed (the skin underneath the nail). This is usually a result of inflammation, and often the inflammation around the nails needs to be treated before the infection can be addressed.

Tinea versicolor skin infections lead to scaly patches that vary in colour from white to brown. The patches are usually found on the chest, stomach, or neck and may also be found on the face. The affected areas do not tan, so the infection may only be noticeable in the summer. The rash is usually not itchy.

A dermatophyte infection of the skin produces a red, scaly rash that is often round and may be clear at the centre. In more severe cases, there may also be blisters in the affected area. The rash may be itchy.

Dermatophyte nail infections cause the nails to become dull, thickened, and discoloured. Eventually the nail separates from the toe and may fall off. These infections are more common on the toenails than the fingernails.

Making the Diagnosis

To make a diagnosis, your doctor will ask about your diet and recent use of antibiotics or medications that can weaken the immune system. Your doctor will also consider any history you may have of diabetes, cancer, HIV, or other chronic diseases. These factors can increase your risk of yeast infections.

Yeast infections are easy to identify. The yeast can be seen under the microscope after being scraped off the affected area. However, since yeast is normally there anyway, your doctor will want to confirm that it's Candida albicans causing the problem and not something else.

Dermatophyte and tinea versicolor infections can be diagnosed after scales have been scraped off and examined under the microscope.

Treatment and Prevention

To help minimize your risk of developing a yeast or dermatophyte infection on the skin, try a few of these tips:

• keep your skin dry
• keep your skin clean
• wear loose-fitting cotton clothing to allow air to circulate
• avoid direct contact with a person with a yeast or dermatophyte infection on the skin
• wear gloves whenever you are gardening
• avoid sharing personal items like nail clippers or socks
• try to lose weight to eliminate excess skin folds

If you have a yeast or dermatophyte infection of the skin, your doctor can recommend an antifungal cream or powder. Antifungal shampoos may be recommended for infections affecting the scalp. In cases where an infection covers a large area, is hard to get rid of, or keeps coming back, your doctor may recommend an antifungal pill.

Fungal infections of the nails can be harder to treat and may require several months of treatment. These types of infections usually require a prescription for an antifungal pill. An antifungal nail lacquer is also available for treating certain fungal nail infections (caused by the fungus T. rubrum) in mild to moderate cases where the "moon" of the nail is not infected.