We look at what fungal skin infections are, what they are caused by and how to treat them.

Fungal skin infections are caused by certain types of fungus, or excessive growth of normally harmless types. Fungal skin infections usually affect your skin because they live off keratin, a protein that makes up your skin, hair and nails. Most fungal skin infections can be treated effectively.

Types of fungal skin infections and the symptoms they can cause

Many common fungal infections are superficial, which means they affect the outer layers of the skin, your nails and your hair. These infections include those caused by dermatophyte fungi and by yeasts.

Dermatophyte infections
Most basic superficial fungal skin infections are caused by dermatophytes and include the following.

• Athlete's foot (tinea pedis and tinea manuum). It is estimated that around 1 in 20 Australians have athlete's foot (tinea pedis). Symptoms include itchy, dry, scaly and red skin. There may also be an odour. Sometimes your skin blisters and cracks, which can introduce bacterial infections. The infection is especially common between your toes, where your skin is warm and moist. You often pick up athlete's foot from coming into contact with contaminated skin left behind in swimming pools, showers and saunas. If you don't wash your hands after touching a contaminated area, it can spread to your hands where it's known as tinea manuum. This mostly affects the creases on your palms and sides of your fingers.
• Nail infections. Onychomycosis is the name for any fungal nail infection. Tinea unguium (ringworm of your nails) is a common dermatophyte infection. Your nails can become malformed, thickened and crumbly and turn yellowish white – the symptoms you experience will depend on the fungi causing the infection. If left untreated it can lead to total nail destruction. Not all nails affected like this are caused by fungal infections, but it's a common cause. Toenail infections are commonly linked with athlete's foot. Your fingernails can be affected too.
• Ringworm of the groin (tinea cruris). This is often called 'jock itch' because it occurs in sports people and is common among young men. It causes an itchy, red rash in your groin and the surrounding area that may be painful. It’s usually seen in men who’ve been sweating a lot. Often you’ll also have athlete's foot, as the infection can be spread by scratching your groin after scratching your infected feet.
• Ringworm on the body (tinea corporis). This often affects exposed areas of your body, such as your abdomen (tummy) or your limbs, causing red raised or flat round patches and rings that can merge, grow and spread from the centre. The rings are scaly at the edge surrounding clear skin in the middle.
• Ringworm of the scalp (tinea capitis). This usually affects young children. It can cause hair loss (sometimes leaving the hair shaft behind, which look like black dots in the bald patch). It also causes dry, itchy, scaly areas on your scalp. You may develop painful swollen patches on your scalp that ooze pus (kerion), or develop large yellow crusts. You can also be infected by this fungus without developing any symptoms, and become a carrier instead, spreading the infection to others.

Yeast infections

Yeasts are another type of fungus that can cause skin infections, including the following.

• Thrush. The yeast Candida albicans usually lives naturally in your mouth and digestive system and rarely causes problems. However, in certain situations, such as if you're ill, have poorly managed diabetes, are pregnant or using antibiotics, the fungi multiply too much and can cause thrush symptoms.
  Thrush can affect your mouth and other areas lined with a mucus membrane such as your vagina. Thrush infection often looks like small white patches, which leave a red mark when rubbed off. Vaginal thrush can cause itchiness and a thick, white discharge. Thrush sometimes affects the penis, often causing an itchy, burning red rash on the head of the penis (glans) that may be painful. 
  It also commonly affects newborn babies in the mouth (oral thrush) where the white patches may be mistaken for breast or formula milk. It isn't usually serious, but babies with thrush in their throats may stop feeding properly. Babies may also develop thrush in the nappy area.
• Intertrigo. This is also caused by the normally harmless yeast Candida albicans spreading to your skin. It affects areas where skin touches skin and the environment is warm and moist, such as your armpits, groin, and under heavy breasts or fat folds. It can cause itching, soreness, spots and scales, creating a white–yellow curd over the infected area.
• Pityriasis versicolour. This infection is usually caused by overgrowth of the Malassezia yeasts that live on your skin.  It causes dark patches or light patches on skin. It usually affects your chest, back, neck and/or arms. Another name for this condition is tinea versicolor (versicolor means 'of various colours'). 

Causes of fungal skin infections

You're more at risk of getting a fungal skin infection if you:

• smoke
• have recently taken a course of broad-spectrum antibiotics
• are taking steroids
• have high blood glucose levels (for example, if you have diabetes that isn’t managed well)
• are overweight
• have had fungal skin infections in the past or have an existing underlying skin condition such as psoriasis
• have a weakened immune system caused, for example, by cancer or HIV/AIDS.

Moist skin encourages fungal skin infections. This means you're more likely to pick one up if you don't dry your skin properly after sweating or bathing, or if you wear tight clothes that don't allow sweat to evaporate. Damage to the surface of your skin, such as a cut or graze, can also encourage fungi to grow.

How do fungal skin infections spread?

Fungal skin infections can be spread from person to person. For example, athlete's foot is thought to be spread in communal areas, such as gyms and swimming pools. Contact with bed sheets or towels and personal items such as hairbrushes can also spread fungal infections. It's also possible to catch some fungal infections from animals such as cats or dogs, and, more rarely, cattle.

Ringworm is occasionally caught this way.

Diagnosis of fungal skin infections

Your GP will ask about your symptoms and examine you, looking at the appearance and location of your rash. They may also take a skin scraping, or a fragment of your nail or hair, and send it to a laboratory for testing, to confirm the diagnosis.

Treatment of fungal skin infections

As most fungal skin infections are on the surface of your skin, you’ll usually be able to apply topical antifungal treatments directly onto your skin in the infected area.

There are a variety of treatments available in the form of creams, lotions and medicated powders. Some treatments are available over-the-counter from a pharmacist. For example, there are sprays available for treating athlete's foot and antifungal shampoos for scalp infections. Ask your pharmacist for advice.

However, if the infection covers quite a large area of your skin, or affects your nails or scalp, your GP may give you a prescription for a stronger medication, which is often in tablet form.

These treatments are usually effective. They can occasionally cause side effects which may include skin irritation for topical treatments. It isn't unusual for your infection to return, even when it seems to have been treated. You’ll usually be advised to keep using topical treatments for two weeks after symptoms have disappeared. You may need to take some treatments for a few weeks, or up to a year or so for toenail infections.

If you're buying an over-the-counter antifungal treatment, you need to be sure that you have a fungal infection. Sometimes a new rash may look like a previously diagnosed fungal infection. If over-the-counter treatments don't seem to work or you have any concerns about your skin condition, see your GP.

Prevention of fungal skin infections

There are some steps you can take to reduce your risk of getting a fungal skin infection.

• Drying your skin carefully after bathing
• Wearing loose fitting clothes and underwear
• Choosing cotton socks and natural fibre underwear to allow your skin to breathe
• Not sharing towels, hair brushes, and combs
• Washing bed linen and clothes often to get rid of fungal spores
• Disinfecting pillows, hats, combs or scissors if someone in your family has scalp ringworm
• Always wearing thongs or plastic shoes in communal areas such as swimming pools and change rooms
• Alternating shoes every two or three days so that they have time to dry out (to help prevent athlete's foot)
• Wearing synthetic fibres that 'wick' the sweat away from the body, helping to keep your skin dry if you're exercising.

If you have diabetes, you need to keep manage your blood glucose levels to keep them within an ideal range for you as discussed with your health professionals, as consistently raised blood glucose levels can increased your risk of developing bacterial and fungal skin infections.