Athlete's foot

Disease Description (Causes and Symptoms)

• Definition: Tinea pedis (athlete’s foot) is an infectious skin disease mainly affecting the feet, caused by dermatophytes (fungi), and may also involve the fingernails and toenails (nails).
• Causes and pathophysiology: Dermatophytes (mainly species of the genus Trichophyton) penetrate the stratum corneum, break down keratin, and proliferate. Transmission is more likely in humid, enclosed environments (sweaty feet, tight shoes) and through public bathhouses, swimming pools, shared towels, etc. It may become more severe or recur frequently in the presence of underlying conditions such as skin damage, immunosuppression, or diabetes.
• Main symptoms: Itching (pruritus), cracks and peeling between the toes (interdigital type), small blisters (vesicular type), hyperkeratosis and thickening of the soles and sides of the feet (hyperkeratotic or moccasin type), blisters, and skin scaling; sometimes pain and exudate (in cases of secondary bacterial infection). Types commonly occur in combination.

Treatment Methods (Standard Treatment·Self-Care·Precautions)

• Diagnosis: Confirmed by clinical findings plus a KOH (direct smear) test or fungal culture. Differential diagnosis from conditions such as eczema is necessary.
• Topical treatment (first-line treatment for most cutaneous forms of athlete’s foot)
  • Use topical antifungal agents (e.g., allylamine agents such as terbinafine ointment, imidazole/azole agents, etc.). Generally, continue applying for an additional 2–4 weeks after symptoms disappear (up to 2–6 weeks depending on standard recommendations and the type of lesion) to reduce recurrence.
  • Application method: Apply regularly to the affected area and surrounding skin (follow the product-specific instructions).
• Systemic treatment (considered in the following cases)
  • Oral antifungal agents may be necessary when the infection is widespread or frequently recurrent, involves the nails, causes extensive or severe inflammation, or occurs in an immunocompromised patient.
  • Representative medications and usage examples (determined at the physician’s discretion): terbinafine 250 mg PO once daily (2–6 weeks for cutaneous forms); for onychomycosis, terbinafine 250 mg PO once daily for nail treatment: 6 weeks for fingernails and 12 weeks for toenails; itraconazole pulse therapy (as prescribed by a physician), etc.
  • Liver function tests may be necessary during systemic treatment (especially in cases of pre-existing liver disease or use of hepatotoxic medications).
• Supportive and lifestyle management
  • Wash the feet frequently (at least once a day, and more often if they sweat heavily) and keep them completely dry, including between the toes (gently dry with a towel or use a hair dryer on a low setting).
  • Wear well-ventilated shoes and sweat-absorbing socks (cotton or moisture-wicking materials); dry shoes and alternate between pairs. Avoid old shoes used for a long time and other people’s shoes.
  • Wear slippers in public places (bathhouses and swimming pools) and use personal towels. Consider disinfecting shoes, socks, and floors (with antifungal spray or by washing).
• Precautions and risk of complications
  • Topical corticosteroids used alone may worsen fungal infections; therefore, do not use corticosteroids alone when athlete’s foot is suspected.
  • Systemic antifungal agents may cause adverse effects such as hepatotoxicity (elevated liver enzyme levels and drug interactions), so follow the physician’s instructions and undergo required tests (such as liver function tests). Administration may be restricted during pregnancy or breastfeeding.
  • Complications: Secondary bacterial infections (impetigo and cellulitis), chronic hyperkeratosis and thickening, nail involvement, and chronic disease due to delayed treatment. Patients with diabetes or peripheral vascular disease have an increased risk of bacterial complications.

Checklist Before an Outpatient Visit (Items to Bring·Problem Log and Example Questions)

• Items to bring/pre-visit records
  • A list of all medications currently being taken (including prescription drugs, OTC medications, and supplements).
  • Previous diagnosis and treatment records (including a history of antifungal use and records of its effects and adverse effects).
  • Medical history: diabetes, liver disease, immunocompromised conditions (such as taking steroids or immunosuppressants), and pregnancy status.
  • When symptoms began and their progression (if photographs are available, take them and bring them), and factors that worsen symptoms (specific shoes or environments).
  • Whether the toenails are involved, and whether pain, fever, or exudate (pus) is present.
• Examples of materials to show the doctor during the outpatient visit
  • Photographs of the affected areas (from various angles), photos of medications and products used and the duration of use, and recent temperature and glucose levels (for patients with diabetes), if possible.

Examples of General Questions to Ask the Doctor

• What is the expected treatment duration and what are the side effects of this medication (the prescribed antifungal)?
• Will topical treatment be sufficient, or will oral medication be necessary? What are the criteria?
• Are liver function tests or other tests necessary? When should the tests be performed?
• What lifestyle changes or additional preventive measures can help reduce recurrence?
• Do family members (household contacts) need to be tested or treated?

Examples of Disease-Specific Questions

• The infection has spread to the toenails (nails). Given the current condition, is oral treatment (e.g., terbinafine) necessary, and if so, what are the expected treatment duration and monitoring plan?
• I have diabetes (or am immunocompromised). What additional precautions should be taken to prevent and treat secondary infections caused by athlete’s foot?