Athlete's foot is a form of dermatophytosis (fungal infection of the skin), caused by dermatophytes, fungi (most of which are mold) which inhabit dead layers of skin and digests keratin.[2] Dermatophytes are anthropophilic, meaning these parasitic fungi prefer human hosts. Athlete's foot is most commonly caused by the molds known as Trichophyton rubrum and T. mentagrophytes,[21] but may also be caused by Epidermophyton floccosum.[22][23] Most cases of athlete's foot in the general population are caused by T. rubrum; however, the majority of athlete's foot cases in athletes are caused by T. mentagrophytes.[13]
“The medications we use to treat this are expensive and they are not benign,” cautioned Dr. Hinkes. “Lamisil is so powerful it stays in your body six months after you stop using it, and that’s one of the reasons why it works so well. So when we use these medicines, we have to be conscious that we may be affecting a person’s liver, because the liver is the organ that helps to detoxify the body and excretes that medicine.”
Athlete’s foot—the most prevalent foot fungus—thrives in warm, sweaty places like the insides of your athletic shoes, which is how it got its name. However, foot fungus can develop in multiple environments, natural and man-made, as long as there is lots of moisture where fungi can grow. These include shared areas at gyms or pools, soil and grass, or even shared items such as shoes, socks, or towels from household members who are infected.  
Medical treatment of onychomycosis is suggested in patients who are experiencing pain and discomfort due to the nail changes. Patients with higher risk factors for infections such as diabetes and a previous history of cellulitis (infection of the soft tissue) near the affected nails may also benefit from treatment. Poor cosmetic appearance is another reason for medical treatment.
The vesiculobullous type of athlete's foot is less common and is usually caused by T. mentagrophytes and is characterized by a sudden outbreak of itchy blisters and vesicles on an erythematous base,[7] usually appearing on the sole of the foot. This subtype of athlete's foot is often complicated by secondary bacterial infection by Streptococcus pyogenes or Staphylococcus aureus.[13]
Dermatophytes — fungus that grows on the skin, hair and nails but don’t penetrate tissues of the body. Athlete’s foot or Trichophyton rubrum is the most common dermatophyte and can actually infect the toenails. Infection can also begin by touching objects that have dermatophytes on them, such as nail clippers, nail files, socks, shoes, shower floors, etc. Dermatophytes are the cause of most fungal toenail infections.
Red or black nails due to a hematoma, or blood under the nail, usually occur from trauma (like whacking yourself on the thumb with a hammer). The discolored area will grow out with the nail and be trimmed off as you trim your nails. If you have a black spot under your nail that was not caused by trauma, you may want to see a dermatologist or a podiatrist if it involves a toenail to make sure it is not melanoma (a type of skin cancer associated with pigmented cells). A simple biopsy can rule out malignancy (cancer).
Use soap and water to wash your feet, and dry well, including between toes. Trim your toenails -- straight across -- to keep them shorter than the end of your toe. Make sure the tools you use are clean, too. Wash clippers and files with soap and water, then wipe with rubbing alcohol. You might be tempted to cover up discolored nails with polish, but don't. Your nail bed can't "breathe," which keeps fungus from going away.
×