What caused this highly pruritic rash that resists OTC remedies?

Case 1:
After 6 weeks of scratching a very itchy, worsening rash on his left leg, a 53-year-old man seeks medical evaluation. He has tried over-the-counter (OTC) topical remedies with no success. The patient is otherwise healthy and takes no medications.

What do you suspect?

A. Cellulitis.
B. Tinea corporis.
C. Contact dermatitis
D. Urticaria.
E. Creeping eruption.

A potassium hydroxide evaluation confirmed suspected tinea corporis, B. Cellulitis tends to be more painful than pruritic. The duration of both contact dermatitis and urticaria is days, not weeks. This patient did not have gyrate lesions without central erythema, which are typical of creeping eruption.

OTC agents may exacerbate dermatophyte infections. This patient contracted the dermatophyte from the household pet, a cat who rubbed up against his leg. Because the eruption was extensive, a systemic antifungal medication was prescribed; the infection resolved completely. The patient was advised to treat the cat as well by bathing the animal with OTC shampoo.