What is athletes foot? |
Athlete's foot is also known as tinea pedis, moccasin type tinea and/or ringworm of the feet.
What causes disease?
Athlete's foot is a fungal infection (ie. caused by fungi- not bacterial or viral) of the foot caused by a type of fungus called dermatophytes. These are a group of fungi which are able to live in dead skin. Ringworm is also caused by dermatophytes and as such the two disorders are very closely related.
Skin is made of a number of layers. The outer layer is known as the epidermis. This is continuously producing new skin cells from it's base to replace the outer cells which are being rubbed off. Much like a tree loses its bark so to do we lose skin; however, there are always new layers beneath to replace what is lost. The epidermis is approximately 0.05mm thick. Beneath the epidermis is the dermis. This is 1 to 2 mm thick and contains the nerves and blood vessels for the skin.
Lying over the epidermis (ie. in contact with the air) is a layer of keratin. This is a tough non-living layer which is like our bodies 'varnish.' It is specially made to withstand the constant rubbing it is exposed to. Dermatophytes live in this layer of keratin. Dermatophytes make a substance known as keratinase which can digest the surrounding keratin (much as food in our stomach and intestines is digested by acid and enzymes). This enables them to live in keratin however it also triggers the bodies own defence mechanisms. Unfortunately for us because the layer of keratin is essentially 'dead' it is very difficult for our body to remove the infection (as the body's defences cannot easily travel into the 'dead' tissue). This leads to an annoying chronic (ie. long term) infection.
It is thought that athlete's foot is mostly acquired from walking barefoot on surfaces which are contaminated with the fungi. Showers, gymnasiums and changing rooms are all thought to be likely areas for acquiring athlete's foot. In direct contradiction to this though are some studies in which people have been infected with the fungus however have not developed athlete's foot. So there must be another reason why some people acquire athlete's foot and others don't.
There are also a number of factors which favour athlete's foot, making the infection worse and treatment more difficult. These include:
- Humid environments
- Occlusion (ie. wearing socks or occlusive shoes for long periods)
- Athlete's foot is probably the most common dermatophyte infection in the World with up to 70% of the population having had this infection.
- Males are affected more than females.
- The risk of getting athlete's foot increases with age. Most cases occur after puberty. Infection is most common between the ages of 20 and 50 years.
What are the symptoms?
Acute onset of athlete's foot is characterised by a red rash which may have small fluid filled blisters associated (vesicles). This rash usually occurs between the toes however may also extend across the sole of the foot into the instep.
This rash can be intensely itchy and may also be painful. These acute episodes usually disappear on their own however often recur again in the future. Chronic (long-term) athlete's foot may follow straight on from an acute (short-term) infection, however more often is a slowly progressive red, scaly, itchy rash which comes on after the acute infection has seemed to get better. This also affects the spaces between the toes and can occasionally spread onto the top or bottom of the foot. Cracks or fissures commonly occur between the toes in chronic athlete's foot.
The dermatophytes causing athlete's foot can also infect other parts of the body (including hair and nails). There is a condition known as "one-hand, two-feet disease" when the dominant hand (which is used for itching) also becomes infected.