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Tinea pedis is a superficial infection of the feet with dermatophytes, a subset of fungus that lives off of the keratin in the skin. It is the most common fungal infection of the body, and is typically characterized by a burning, tingling, or stinging feeling in the feet and toes. Tinea pedis may also be referred to as athlete’s foot.
Tinea pedis is often broken down into four distinct entities. The first is chronic tinea pedis, which is most classically described as a silvery, scaly appearance of the bottoms of the feet, in a moccasin-like appearance. This means that the extent of the infection is diffusely spread across the entire plantar surface of the foot, and commonly expands up into the toes and the sides of the foot, where a moccasin may come in contact with the skin. The organism that most commonly causes this form of tinea pedis is trychophyton rubrum, or t. rubrum.
Another distinct form of tinea pedis is the vesiculobullous or acute vesicular form. This condition is most commonly caused by the organism trychophyton mentagrophytes (t. mentagrophytes). In addition to the burning, tingling, or stinging sensations associated with tinea pedis, the acute vesicular form will also show very small blisters, typically in the arch of the foot. This form of tinea pedis shows acute inflammation, and is often treated with a topical steroid as well as a fungicide.
Acute interdigital tinea pedis is also a common form caused by t. mentagrophytes, and is seen in between the toes, extending down onto the bottom of the feet towards the ball of the foot. This condition may or may not be inflammatory. When acute inflammation is present, a steroid/fungicide combination may also be used for treatment.
Acute interdigital tinea pedis may progress to the more serious but less common ulcerative tinea pedis. Ulcerative tinea pedis occurs when a case of untreated interdigital or vesicular tinea pedis causes severe breakdown of the skin, and a secondary bacterial infection ensues. This bacterial infection superimposed on a fungal infection can cause a great amount of skin loss on the bottoms of the feet, and can lead to a disabling condition. Treatment typically involves a fungicide/steroid combination as well as oral antibiotics.
With the exception of the more serious ulcerative form, most cases of tinea pedis are successfully treated with topical medications. Topical medications consist of a fungicide with or without a very low dose of steroid. The steroid is included in forms of tinea that include inflammation, and serves to decrease some of that inflammation. However, in cases without inflammation, a steroid should not be used so as to avoid the unnecessary side effects associated with steroids. In cases such as chronic tinea pedis, a plain fungicide will suffice.
Patients with severe inflammatory tinea pedis or a case that has not responded to topical treatment after at least one month may be considered for oral medications. Oral medications do come with inherent risks, in particular the risk of liver damage. Blood work is performed before oral anti-fungal medications are prescribed for tinea pedis and/or fungal nail infections.
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