Background and History


You don't have to be an athlete to have athlete's foot. But, it is spread in warm moist places like locker rooms. Athlete's foot is also known as tinea pedis. Tinea is from a latin word that means maggot or grub and pedis refers to the foot. Although tinea pedis was not described in the literature until the 19th century, the ancients thought that similar problems were created by worms which resulted in the older term "ring worm" for tinea corporis, a fungal infection of the body or tinea capitis, a fungal infection of the scalp.

Athlete's foot is caused by a fungous or a type of mold and less often by a yeast. Fungous flourishes in dark, warm, moist environments. Shoes, being an occlusive covering of the foot, and dark, warm and moist can be like a fungal heaven.

“Shoes... being dark, warm and moist can be like a fungal heaven.”

Clinical Appearance


Athlete's foot can appear as cracked and peeling skin between the toes or on the bottom of the foot. It is often itchy but not always. Sometimes one only sees flaking, scaling, dry skin that most people think is just a bit of excessive dryness but in reality is evidence of athlete's foot. Small blisters may occur in conjunction with some fungal infections.

Between the toes the skin can become macerated or excessively soft and mushy. The fungous can go deeper into the skin and through cracks or breaks in the skin bacteria can enter and cause a more troubling secondary bacterial infrection.

Many authorities classify dermatophytic (skin) fungal infections of the foot as follows:

  • Interdigital
    • Between the toes, with scaling, fissuring or softened, macerated skin.
    • Organisms: T. rubrum. Occasionally T. mentagrophytes var interdigitale, and E. floccosum. Sometimes Candida albicans can grow concommitantly or there may be a secondary bacterial infection.
    • Photographic Image
  • Mocassin Type or Hyperkeratotic
    • Bottom of the foot. May itch or be asymptomatic.
    • Organisms: T. rubrum. Sometimes T. mentagrophytes var interdigitale, E. floccosum, Scytalidium hyalinum and S. dimidiatum.
    • Photographic Image 1
    • Photographic Image 2
  • Vesicular
    • Small blisters. Clear or opaque fluid. May lead to secondary bacterial infection.
    • Organisms: Usually T. mentagrophytes var mentagrophytes.
  • Ulcerative
    • Rapidly spreading, with blisters (vesiculopustular lesions) and a secondary bacterial infection
    • Organisms: Usually T. mentagrophytes var mentagrophytes.

 

Prevention


As with many things, the best cure is prevention, so we will start with an approach to limiting your risks of contracting athlete's foot. Since moisture is a risk factor, keeping your feet dry is important. Make sure you dry your feet carefully after showers. In the locker room, you might consider wearing shower sandals to limit exposure to any areas contaminated with fungous. Be careful to dry between your toes and make sure your feet are dry before putting on your socks. You may

“...cotton socks hold moisture against the foot and does not allow the moisture to readily evaporate.”

sprinkle an anti-fungal foot powder in your shoes or on your feet.


Another important thing to remember is that cotton socks hold moisture against the foot and does not allow the moisture to readily evaporate. Athletes performing endurance sports should make sure that they wear socks that are made of non-cotton material that wicks the moisture away from the foot.

Taking a quick look at why the feet end up so moist we find lots and lots of sweat glands between the toes and on the soles of the feet. The highest concentration of sweat glands are in the palms of our hands and the soles of our feet. There are between 2 and 4 million sweat glands over our entire body. Each sweat gland is small and weighs little, but all together they weigh as much as one kidney, about 100 grams. An individual can perspire up to several liters per hour and up to 10 liters per day.

The sole actually has the most sweat glands with 620/cm2. The back has the least with64/cm2. The soles of the feet alone have between 250,000 to 300,000 sweat glands in total.

“...the soles of the feet alone have between 250,000 to 300,000 sweat glands in total..”

Prevention Summary:

  • Keep Your Feet Dry
  • Change your socks often
  • Don't wear cotton socks for sports
  • Use Synthetic Fiber Socks That Wick Off Perspiration
  • Use Anti-fungal powder if needed
  • Change Socks During The Day

Treatment

Mild fungal infections may be treated with over the counter medicine that is readily found in your pharmacy. You may ask the pharmacist for his advice. More difficult to eliminate fungal infections will require prescription strength medicine.Make certain that you follow the directions for prevention to avoid a recurrence and to speed up elimination of the fungal infection. Keeping your feet dry is one of the keys to eliminating and preventing reinfection.


Details for physicians and students:

Differential Diagnosis Of Tinea Pedis:

Many problems related to moisture and warmth many be thought to be tinea pedis but are distinct clinical entities unto themselves. Some of the other clinical entities to consider include:

  • also known as: pompholyx, vesicular palmoplantar eczema. Original thoughts were that this was a disorder of sweat glands. Current theory is that it may be related to atopy, but uncertainty about the origin of dyshidrotic eczema.
  • A chronic dermatitis caused by the bacteria Corynebacterium minutissimum, a normal component of the skin flora.

    Diabetes Mellitus, Hyperhidrosis (excessive perspiration), Weak Cutaneous Barrier, Obesity, and immunocompromised state.

    Evidence based therapy of erythrasma.

  • Erythrasma - Right Axilla (image)

    Treatment: Erythromycin, Lotrimin, others see evidence based resources above.

Antifungal Medications for tinea pedis:

Evidence Based Therapy From Medline see for authoritative and complete listing of medical therapy of fungal infections.

Terbinafine (Lamisil) is an allylamine antifungal. Selectively inhibits an early step in fungal cell membrane sterol synthesis. This interferes with the synthesis of the cell membrane and causes an accumulation of squalene which is toxic to the cell. It is a fungicidal agent

Econazole nitrate (Spectazole Cream) imidazole antifungal. Interferes with RNA and protein synthesis and metabolism. Disrupts fungal cell wall membrane permeability. Fungicidal.

Clotrimazole (Mycelex, Lotrimin) Imidazole broad-spectrum antifungal agent. Imidazole antifungal.Inhibits growth of yeast by altering cell membrane permeability, causing death of fungal cells. Fungacidal.

Ketoconazole (Nizoral) cream - Imidazole broad-spectrum antifungal agent. Affects cell wall growth. Inhibits synthesis of ergosterol, affecting membrane permeability. Fungicidal.

Oxiconazole (Oxistat) cream - Imidazole broad-spectrum antifungal agent. Cell wall synthesis inhibited by inhibition of biosynthesis of ergosterol. Membrane permeability impacted. Fungicidal.

Naftifine (Naftin) cream and gel - allylamine derivative; Broad-spectrum. Decreases the synthesis of ergosterol.


Brief overview of mycology for physicians and students:

Mycology is the study of fungal organisms. The term mykos is a greek word which means mushrooms. There are over 100,000 species of fungal organisms of which only around 300 have been identified as causing human or animal disease with about a 10 - 12 of them causing 90% of human fungal

Fungal organisms are eudaryotes and contain at least one nucleus, nuclear membrance, endoplasmic reticulum, ribosomes and mitochondrium. Fungous cells are not able to perform photosynthesis. Fungal organisms are naturally found in water, soil, and decaying organic matter.

Yeasts and molds

There are two forms of fungal orgamisms: yeasts and molds. Yeasts are a unicellular growth form. The shape is sperical or ellipsoidal while their size is from 3 to 15 micrometer in diameter. Most of these yeasts reproduce by budding, although binary fission is sometimes observed.

Molds grow as a multicellular and filamentous colony. Growth occurs by apical elongation or extension from the tip of the hyphae. Molds grow on surfaces with some hyphae penetrating deeper which are called vegetative or substrate hyphae.

Dimorphic Species

Some species of fungi can grow in both the yeast and mold form dependent upon environmental conditions. Cryptococcus is an example of a yeast like form. Histoplasma is a dimorphic form which makes hyphae at environmental temperatures and yeast cells at body temperature. Candida is a dimorphic species that does the reverse with filamentous form at body temperature and yeast cells in the environment.

Fungal Diseases

Two disease types are noted: superficial mycoses occurring in the skin, hair and nails, and deep mycoses affecting the deeper structures and internal organs. Fungi are usually free living organisms that may be acquired as infecting organisms through cuts or by inhaling. Candida is a part of the normal skin flora and is more apt to cause infection in immune compromised individuals. Mycetoma is considered to be caused by a subcutaneous fungous and not a deep infecting organism.

Cellular Structure

Fungal cell walls function as antigens. Individuals differ in their production of antibodies to fungal organisms and this is one of the origins of differring susceptability to dermatophytic infections. The cell wall makes up about 90% of the dry weight of the fungal cell. Over 80% of the cell wall is carbohydrate. A small amount of polysaccharides are also found in fugnal cell walls.

References:

Skin Disorders Of The Foot, The Physician And Sportsmedicine, Vol 27, No. 2 February 1999

Skin Care for Active People Michael L. Ramsey, MD The Physician And Sportsmedicine - Vol 25 - No. 3 - March 97

EMedicine Online Text: Tinea Pedis