Tinea pedis

What is tinea pedis?

Tinea pedis is a foot infection due to a dermatophyte fungus. Tinea pedis thrives in warm humid conditions and is most common in young adult men.

Tinea pedis is most frequently due to:

• Trichophyton (T.) rubrum
• T. interdigitale, previously called T. mentagrophytes var. interdigitale
• Epidermophyton floccosum

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Clinical features of tinea pedis

Tinea pedis has various patterns and may affect one or both feet.

• Chronic hyperkeratotic tinea refers to patchy fine dry scaling on the sole of the foot
• ‘Moccasin’ tinea is extensive hyperkeratotic tinea, in which the skin of the entire sole, heel and sides of the foot is dry but not inflamed. The affected area does not include the top of the foot. This is usually caused by T. rubrum.
• Athlete's foot i.e. moist peeling irritable skin between the toes, most often in the cleft between the fourth and fifth toes.
• Clusters of blisters or pustules on the sides of the feet or insteps (more likely with T. interdigitale).
• Round dry patches on the top of the foot (ringworm like tinea corporis).

Factors predisoposing to tinea pedis

Tinea pedis affects all ages but is more common in adults than in children. The fungal spores can persist for months or years in bathrooms, changing rooms and swimming pools. Walking bare foot on a communal floor or sharing a towel can result in infection.

Some people are particularly prone to troublesome tinea pedis. This may be because:

• They are more exposed to the spores at home or during recreational activities.
• Their skin produces less fatty acid (a natural antifungal agent).
• They wear occlusive footwear.
• They wear the same pair of socks or shoes for long periods.
• They sweat excessively (hyperhidrosis).
• They have some form of immunodeficiency e.g. medication such as azathioprine, or infection with human immunodeficiency virus.
• They have poor circulation resulting in cold feet e.g. due to lymphoedema.

Diagnosis of tinea pedis

The diagnosis of tinea pedis is confirmed by microscopy and culture of skin scrapings.

Treatment of tinea pedis

Tinea pedis is usually treated with topical antifungal agents, but if the treatment is unsuccessful, oral antifungal medicines may be considered, including terbinafine and itraconazole.

Resistance of tinea pedis to treatment

If treatment is unsuccessful consider:

• Untreated infection, for example, of the nails (onychomycosis).
• Reinfection from contact with spores in surroundings or clothing.
• An untreated infected family member.
• An alternative explanation for symptoms such as dermatitis or psoriasis 

Moccasin tinea is particularly resistant to treatment.