Fungi are plant-like organisms that may cause infection. There are many different types of fungi that can cause skin infections. Some of these are naturally present in the human body (yeast). Others are foreign particles (dermatophytes) that grow on the body and promote infection.
Fungi grow best in tropical environments. They tend to prefer areas that are warm, moist and dark. In humans, fungi grow well on skin, in skin folds (e.g., breast folds, groin, armpits) or in mucous membranes (e.g., mouth, genitals).
Candidiasis is the most common form of yeast infection. It may affect many organs and body systems (e.g., genitals, respiratory system). Candidiasis can also affect the skin, nails and mouth.
- Thrush. Yeast infection of the mouth. White patches form on the inside of the mouth. Thrush is most common in infants.
- Yeast onychomycosis. Yeast infection of the nails.
- Generalized cutaneous candidiasis. An unusual form of yeast infection with a widespread itchy rash.
- Tinea versicolor. Also called pityriasis versicolor, this common skin infection is caused by yeast. It causes tan, white or erythematous (red) scaly patches on the neck, torso and arms. It is most common in adolescents and young adults.
In addition, individuals with intertrigo, a skin infection that causes inflammation in the body folds, can also be infected with yeast or other fungi, which worsens the condition. When intertrigo is accompanied by a yeast infection, rashes tend to form in the skin folds.
Dermatophyte infections may be caused by a number of different fungi. Dermatophytes digest the protein keratin and may infect areas where the protein is found, such as the skin, hair or nails. The infections are contagious and may be spread by direct contact with people, animals or soil.
Dermatophyte infections are usually classified according to the part of the body they affect. Most forms occur in adolescents after puberty and in adults, but there are exceptions. These infections may or may not produce inflammation, and they may be acute (short-term) or chronic (ongoing) in duration. Common dermatophyte infections include:
Fungal infection of the foot. This is the most common form of dermatophyte infection in the United States, but is rare in populations that do not wear shoes. It is often accompanied by other fungal infections (e.g., jock itch, hand fungus, nail fungus). Athlete’s foot is most often chronic and, left untreated, the condition usually persists indefinitely. The acute form tends to go away on its own, but may recur frequently. Athlete’s foot is more frequently found in males, and uncommon in children before puberty.
Also called tinea circinata and tinea glabrosa. Ringworm can appear anywhere on the skin surface, but most commonly occurs on exposed skin, such as the hands and arms. It often results from the spread of dermatophytes from other infections (e.g., athlete’s foot, tinea capitis). Ringworm is common among all age groups, but it is especially common among children.
May also be referred to as gym itch, dhobie itch or eczema marginatum. This is an infection in the groin area. Jock itch is often caused by the spread of athlete’s foot when clothing that has come into contact with infected feet touches the groin region. It is most common in men.
Dermatophyte infection of the nails. This usually begins in a nail that has been injured and may spread to other (even all) nails. The toenails are affected more often than the fingernails. In fact, fingernail infection rarely occurs without a previous toenail infection. Dermatophyte onychomycosis is often associated with other fungal infections (e.g., athlete’s foot, ringworm).
Onychomycosis is the most chronic and difficult-to-cure dermatophyte infection. It may persist indefinitely if not treated. The infection may be on the nail bed or on the surface of the nail itself. It usually begins at the edge of the nail and progresses towards the cuticle, but it may also begin at the cuticle. It is most common in adult men.
Also called ringworm of the scalp. Most cases are caused by a fungus called tinea tonsurans. It occurs almost exclusively in children and some forms can be nearly epidemic. Forms of tinea capitis include:
- Black dot type. The most common type of tinea capitis in the United States, found most often in children. It appears as bald patches with multiple black dots.
- Gray patch type. In the United States, this type is usually acquired from animals, and rarely from other humans. It appears as fuzzy gray patches of baldness.
Fungal infection of the palm of the hand and spaces between the fingers. It tends to be chronic and is often associated with athlete’s foot and onychomycosis.
This is an infection in the bearded portions of the neck and face. It was previously more common, but has become less common with the use of disposable razors and the standard sterilization of barber’s tools.
These are superficial fungal, stony growths on the hair shaft, most commonly in the hair of the beard or mustache of men.
This is an infection of the skin on the palms characterized by deeply pigmented, non-scaly patches. Usually, there is no itching.
- Compromised immune system. Yeast infections may occur when the immune system is weakened due to illness, disease (e.g., diabetes), stress or certain medications (e.g., immunosuppressants). A weak immune system can disturb the natural balance of skin organisms and allow one type to overgrow.
- Use of antibiotics. Antibiotic use may also cause yeast infections by killing the natural bacteria that keep the yeast growth under control.
- Tropical climate. Fungi grow best in regions that are warm and humid, so people living in such areas may be more prone to fungal infection.
- Obesity. People who are obese may also be at higher risk because they have many skin folds to encourage fungal growth.
- Heredity. Some individuals may be more susceptible to fungal skin infections due to genetic predisposition.
- Pre-existing injury or infection. People are more likely to develop fungal infections when they have pre-existing skin injury, nail injury or infection.
- Poor hygiene. A lack of hygiene can promote the growth of fungus on the skin and nails.
Continuous exposure to water may predispose an individual to fungal infections, as well as manicures and pedicures.
In addition, dermatophyte fungal infections may be caused by direct contact with infected humans, animals, contaminated objects or soil.
The signs and symptoms of fungal skin infections vary depending on the type of infection present. Signs and symptoms of yeast (candidiasis) infections, by type, include:
- Thrush. White patches form inside the mouth. These bear a resemblance to cottage cheese.
- Yeast infection associated with intertrigo (a skin condition that causes inflammation). Localized, bright red rash at skin folds. The border of the rash is generally scalloped, with a white rim that may contain small bumps filled with pus (pustules). Scaling typically occurs and may be accompanied by mild to intense itching (pruritus) or burning. The rash may also soften and break down the skin and spread to other regions.
- Generalized cutaneous candidiasis. A widespread, diffuse rash over the torso and extremities. There is general pruritus that is most severe at the groin and anal region, armpits, hands and feet.
- Yeast onychomycosis. Pain, redness (erythema), inflammation and warmth around and underneath the nail and nail bed, possibly with a discharge of pus. The nails may be thickened, ridged and discolored. Sometimes, the entire nail is lost.
- Tinea versicolor. White, tan or red scaly patches appear on the skin. They typically form on the neck, torso or arms.
Signs and symptoms of foreign fungi (dermatophyte) infections, by type, include:
Cracking and scaling of the skin between the toes, especially the fourth and fifth toe, with pruritus and possibly soreness. It often spreads over the sole and instep of the foot. It may later spread onto the sides or top of the foot and in severe, untreated cases, even over the ankle and leg. Small, fluid-filled blisters may also be present and the border between affected and unaffected skin tends to be very distinct. Athlete’s foot is typically more severe in hot weather, when wearing heavy footwear or when perspiring excessively. One or both feet may be affected. Chronic forms tend to be slowly progressive whereas acute forms may be very sudden and tend to be intensely itchy or even painful.
Red, flat or slightly raised circular sores that may be intensely itchy. These may be dry and scaly or crusted and moist, and may be accompanied by tiny blisters or papules. As the sores become bigger, the center tends to clear, leaving seemingly normal skin surrounded by an infected edge and giving the infection its common name. There are no worms involved in this condition.
A raised, itchy, red rash that occurs at sites of skin-to-skin contact in the groin and anal areas. The scrotum and penis are usually not affected. The borders of the rash are well-defined and scaly and may contain blisters or pustules. The rash increases in size over time.
The affected nail becomes thick, discolored, pitted, grooved and brittle and looses its luster or shine. In some cases, dull white spots form on the nail and may eventually affect the entire nail area. Affected portions of the nail often break away, exposing the nail bed beneath, and remaining portions of the nail become lumped and deformed. The nail may loosen and detach completely (onycholysis). Pain in the toes or fingers, and a foul odor may also accompany the condition.
One or more lesions appear on the scalp, with or without inflammation. Baldness (alopecia) typically occurs. This is usually reversible and may occur in patches or affect the entire scalp. The longer the infection persists, the more likely the hair loss will be permanent. Swollen, raw and pus-filled lesions (kerions) may develop. The forms of tinea capitis have specific signs and symptoms and include:
- Black dot type. Begins as a small patch that slowly enlarges. There is no itching, but there is redness. Hairs break off flush with the scalp and particles accumulate in the follicle openings, appearing as black dots. If left untreated, scars may form.
- Gray patch type. Begins as a small patch that spreads for a while then stops spreading and persists. Redness and scaling are present. Hairs break off just above the scalp level and have a frosted appearance.
Thickened, usually noninflammatory skin on the palms and between the fingers. Often, only one hand is affected.
Circular lesions with scaling in the bearded areas of the face and neck. There may be severe inflammation, pus-filled follicles or abscesses. Bald patches are common, but usually reversible. Scarring may occur.
Fungal nodules or “stones” form along the hair shaft, usually in the beard or mustache. They may fully encompass the shaft like a sheath. Hair breakage may occur.
Usually no itching and only a single lesion on the palm of the hand. Lesions may also occur on the soles of the feet, neck and trunk. They are gray or green with a distinct border and may be velvety or have mild scaling.
The diagnosis of most fungal skin infections involves obtaining the patient’s medical history, as well as performing a physical examination, examining skin scrapings and fungal cultures. However, a biopsy of the affected skin, nails or hair is occasionally performed as well.
Most forms of fungal skin infections can be cured quickly and easily if they are treated early and properly. However, some infections may be more chronic (ongoing) and difficult to treat. Infections may also come back after treatment.
Treatment decisions are based on a number of factors including the extent and location of the condition. The patient’s age, overall health and medical history may also influence treatment.
Topical antifungal medications are applied directly to the skin and are usually the first-line therapy for localized fungal skin infections, regardless of their cause (e.g., yeast or other fungi). The azole and allylamine classes of medication are particularly useful. Many effective antifungal creams are available without a prescription and most are applied once or twice a day. It may take several days before a reduction in symptoms is noticed. For minor infections, some physicians prefer topical combinations of corticosteroids and antifungals. Oral antifungals (e.g., griseofulvin, terbinafine) may be required for genital or oral yeast infections or more persistent or chronic infections.
Certain fungal skin infections require specific treatment:
- Tinea capitis. This infection may be particularly resistant. Topical treatments do not work. Therefore, oral antifungals are required.
- Onychomycosis. This is the most difficult fungal infection to treat. Most topical treatments do not work and oral antifungals may need to be used for several months. It can recur despite treatment with oral medicine because people can have an inherited tendency to get it. A topical antifungal nail lacquer, ciclopirox, may be effective. Even if treatment is successful, it may take up to a year for a new, clear nail to grow and replace the old nail.
- Piedra (fungal hair infection). Affected hairs are clipped and the area is washed with an antifungal shampoo.
Antibiotics may also be prescribed to treat secondary bacterial infections that develop as the result of scratching or other factors.
Depending on the severity and location of the infection, patients may have to use medication for weeks, months or longer.
Fungi can remain on the skin long after rashes and other symptoms improve. As a result, it is important for patients to continue treatment as recommended by their physician, despite relief of symptoms.
The most effective method for preventing fungal skin infections is maintaining good hygiene. Some important tips include:
- Keep skin clean and dry. Hands and feet should be washed with soap and dried thoroughly after bathing or swimming, especially between the toes.
- Wash hands immediately after touching an infected nail or area of skin. This can help prevent the spread of fungus from one area to another.
- Wear clean socks and underwear every day. Change socks at least once a day. People who sweat a lot should change their socks more frequently.
- Wash socks, towels and bath mats at high temperatures (140 degrees Fahrenheit [60 degrees Celsius] or higher).
- Alternate shoes daily to let them air out. Shoes should also be taken off sporadically throughout the day, especially after exercise.
- Wear comfortable clothes and shoes. Shoes that are well ventilated (e.g., open toe shoes) and shoes made of natural material, such as leather, are preferable to those that are lined with plastic. Shoes should also provide good support and have a wide toe area.
- Avoid rough-textured, chafing clothing.
- Do not use other people’s personal items, including:
- Sports equipment
- Clean frequently. Showers or bathtubs should be sanitized often with bleach. Bathroom floors and other floors that are frequently walked barefoot on should also be cleaned regularly.
- Use only facilities that are cleaned and disinfected daily, including:
- Locker room
- Public swimming pool
- Avoid walking barefoot in public places (e.g., public shower, public pool). Instead, wear flip-flops or sandals.
- Maintain a healthy weight.
- Use topical antifungal powders as needed.
- Treat illnesses promptly.
Additional prevention methods include:
- Keep fingernails and toenails short. Nails should be cut straight across and thickened areas should be filed down. Avoid trimming and picking at the skin around the nails.
- Use a separate nail trimmer and nail file on healthy nails and infected nails.
- Bring a personal set of instruments (e.g., nail trimmers, nail files) to nail salons.
- Wear gloves. People should wear 100 percent cotton gloves when doing dry work, and waterproof gloves when doing wet work (e.g., washing dishes).
Patients may wish to ask their doctor the following questions about fungal skin infections:
- Do my symptoms indicate that I have a fungal skin infection?
- What kind of fungal skin infection do I have?
- What may have caused me to develop this infection?
- Does this infection pose any danger to my overall health?
- Can I spread this condition to other parts of my body or to other people? If so, what precautions should I take to avoid spreading the infection?
- What are my treatment options?
- How long will my treatment last?
- When can I expect to see an improvement?
- Is it likely I will develop a fungal infection again in the future?
- What can I do to avoid getting another infection after this one is cured?