This patient has pitted keratolysis and should be treated with erythromycin lotion. Pitted keratolysis presents with small indented pits on a background of hyperkeratosis and results from increased sweating or perspiration (hyperhidrosis) of the feet. It is a superficial bacterial infection secondary to Kytococcus sedentarius, Corynebacterium, or Actinomyces spp. First-line treatment includes clindamycin lotion or erythromycin lotion in conjunction with keeping the feet dry. Oral therapy with clarithromycin or erythromycin also can be used.

Topical clotrimazole and other antifungal agents are effective for tinea pedis or candidal infections of the feet, which often have macerated web spaces with superficial scale and erythema. The patient's web spaces were not affected, and the clinical picture is consistent with pitted keratolysis, not tinea pedis.

Clotrimazole-betamethasone cream also is ineffective for pitted keratolysis. The combination of a topical antifungal and a topical glucocorticoid will not improve a superficial bacterial infection and will allow it to worsen. In addition, combination treatment can decrease diagnostic accuracy, as combined agents can treat an underlying entity (fungus), but the topical glucocorticoid may also cause the infection to worsen. Combination treatment may be associated with more side effects at an increased cost.

Another topical glucocorticoid, hydrocortisone, may cause the superficial bacterial infection to worsen and will not treat the underlying infection. Topical glucocorticoids may be used for eczematous dermatitis, but not for pitted keratolysis.