A 6-year-old boy presents with severe pruritus and lichenified plaques over the antecubital and popliteal fossae for the past 3 months. He has a personal history of allergic rhinitis and a family history of asthma. Skin prick testing shows sensitization to dust mites and pollen. Topical emollients and low-potency corticosteroids have provided only partial relief. What is the most appropriate next step in management?