Athlete's foot (also known as ringworm of the foot and tinea pedis, and also Hong Kong footsimplified Chinese: 香港脚; traditional Chinese: 香港腳) in the Chinese world) is a fungal infection of the skin that causes scaling, flaking, and itch of affected areas. It is caused by fungi in the genus Trichophyton and is typically transmitted in moist areas where people walk barefoot, such as showers or bathhouses. Although the condition typically affects the feet, it can spread to other areas of the body, including the groin. Athlete's foot can be treated by a number of pharmaceutical and other treatments.
Etymology
The name "Hong Kong foot" originated from the stationing of the British army in Hong Kong. After the Qing DynastyChina lost in the First Opium War, they ceded Hong Kong to the United Kingdom. Because the British were used to life in less humid climates of Europe, when they came to Hong Kong, which has a hot and moist climate, they were still wearing their military boots without good ventilation resulting in many British soldiers catching an unknown skin disease with many tiny boils. Some were swollen red with pus, and it was very itchy. Yet, at that time the European physicians had never seen this kind of disease, so they thought it was an epidemic in Hong Kong, so they called it "Hong Kong foot".
Signs and symptoms
Athlete's foot causes scaling, flaking, and itching of the affected skin. Blisters and cracked skin may also occur, leading to exposed raw tissue, pain, swelling, and inflammation. Secondary bacterial infection can accompany the fungal infection, sometimes requiring a course of oral antibiotics.
The infection can be spread to other areas of the body, such as the groin, and usually is called by a different name once it spreads, such as tinea corporis on the body or limbs and tinea cruris (jock itch or dhobi itch) for an infection of the groin. Tinea pedis most often manifests between the toes, with the space between the fourth and fifth digits most commonly afflicted.
Some individuals may experience an allergic response to the fungus called an "id reaction" in which blisters or vesicles can appear in areas such as the hands, chest and arms. Treatment of the fungus usually results in resolution of the id reaction.
Diagnosis
Athlete's foot can usually be diagnosed by visual inspection of the skin, but where the diagnosis is in doubt direct microscopy of a potassium hydroxide preparation (known as a KOH test) may help rule out other possible causes, such as eczema or psoriasis.A KOH preparation is performed on skin scrapings from the affected area. The KOH preparation has an excellent positive predictive value, but occasionally false negative results may be obtained, especially if treatment with an antifungal medication has already begun.If the above diagnoses are inconclusive or if a treatment regimen has already been started, a biopsy of the affected skin (i.e. a sample of the living skin tissue) can be taken for histological examination.
A Wood's lamp, although useful in diagnosing fungal infections of the scalp (tinea capitis), is not usually helpful in diagnosing tinea pedis, since the common dermatophytes that cause this disease do not fluoresce under ultraviolet light.However, it can be useful for determining if the disease is due to a nonfungal afflictor.
Transmission
- From person to person
Athlete's foot is a communicable disease caused by a parasitic fungus in the genus Trichophyton, either Trichophyton rubrum or Trichophyton mentagrophytes.It is typically transmitted in moist environments where people walk barefoot, such as showers, bath houses, and locker rooms.It can also be transmitted by sharing footwear with an infected person, or less commonly, by sharing towels with an infected person.
- To other parts of the body
The various parasitic fungi that cause athlete's foot can also cause skin infections on other areas of the body, most often under toenails (onychomycosis) or on the groin (tinea cruris).
Prevention
The fungi that cause athlete's foot can live on shower floors,wet towels, and footwear,and can spread from person to person from shared contact with showers, towels, etc.
Hygiene, therefore, plays an important role in managing an athlete's foot infection. Since fungi thrive in moist environments, keeping feet and footwear as dry as possible, and avoiding sharing towels, etc., aids prevention of primary infection.
Treatments
There are many conventional medications (over-the-counter and prescription) as well as alternative treatments for fungal skin infections, including athlete's foot. Important with any treatment plan is the practice of good hygiene.Several placebo controlled studies report that good foot hygiene alone can cure athlete's foot even without medication in 30-40% of the cases.However, placebo-controlled trials of allylamines and azoles for athlete’s foot consistently produce much higher percentages of cure than placebo.
Medication
Main article: Antifungal drug
Conventional treatment typically involves daily or twice daily application of a topical medication in conjunction with hygiene measures outlined in the above section on prevention. Keeping feet dry and practicing good hygiene is crucial to preventing reinfection. Severe or prolonged fungal skin infections may require treatment with oral antifungal medication. Zinc oxide-based diaper rash ointment may be used; talcum powder can be used to absorb moisture to kill off the infection.
Topical
The fungal infection is often treated with topical antifungal agents, which can take the form of a spray, powder, cream, or gel. The most common ingredients in over-the-counter products are miconazole nitrate (2% typical concentration in the United States) and tolnaftate (1% typ. in the U.S.). Terbinafine is another common over-the-counter drug. There exists a large number of prescription antifungal drugs, from several different drug families. These include ketaconazole, itraconazole, naftifine, and nystatin.
Some topical applications, such as carbol fuchsin (also known in the U.S. as Castellani's paint), often used for intertrigo, work well, but in small, selected areas. This red dye, used in this treatment like many other vital stains, is a fungicide. Nonetheless, good hygiene is the most important in curing athlete's foot.
The time-line for cure may be long, often 45 days or longer. The recommended course of treatment is to "continue to use the topical treatment for four weeks after the symptoms have subsided" to ensure the fungus has been completely eliminated. However, because the itching associated with the infection subsides quickly, patients may not complete the courses of therapy prescribed.
Anti-itch creams are not recommended, as they will alleviate the symptoms, but will exacerbate the fungus; this is because anti-itch creams typically enhance the moisture content of the skin and encourage fungal growth. For the same reason, some drug manufacturers are using a gel instead of a cream for application of topical drugs (for example, naftin and Lamisil). Novartis, maker of Lamisil, claims a gel penetrates the skin more quickly than cream.
If the fungal invader is not a dermatophyte, but a yeast, other medications such as fluconazole may be used. Typically, fluconazole is used for candidal vaginal infections (moniliasis), but has been shown to be of benefit for those with cutaneous yeast infections, as well. The most common of these infections occur in the web (intertriginous) spaces of the toes and at the base of the fingernail or toenail. The hallmark of these infections is a cherry red color surrounding the lesion and a yellow thick pus.
Oral
Oral treatment with griseofulvin was begun early in the 1950s. Because of the tendency to cause liver problems and to provoke aplastic anemia, the drugs were used cautiously and sparingly. Over time, those problems were found to be due to the size of the crystal in the manufacturing process, so microsize and now ultramicrosize crystals were made available with few of the original side effects.
For severe cases, the current preferred oral agent in the UK is the more effective terbinafine.Other prescription oral antifungals include itraconazole and fluconazole.
Alternative treatments
Tea tree oil may improve the symptoms but does not cure the underlying fungal infection.Ajoene, a compound found in garlic, is sometimes used to treat athlete's foot.
