This fungal disease presents with characteristic scaling or cracking of the skin, especially between the toes (interdigital), diffuse scaling over the sole of the foot (dry type), or blisters containing a thin watery fluid; commonly called athlete's foot. In severe cases, vesicular lesions appear on various parts of the body, especially the hands; these dermatophytids do not contain the fungus but are an allergic reaction to fungus products.

Presumptive diagnosis is verified by microscopic examination of potassium hydroxide- or calcofluor white-treated scrapings from lesions that reveal septate branching filaments. Clinical appearance is not diagnostic; final identification is through culture. Note that bacteria, including Gram-negative organisms and coryneforms as well as Candida and Scytalidium species, may produce similar lesions. Itching is often a clue that dermatophyte fungi are present. Scytalidium can also cause similar dry lesions on the sole.