A 4-year-old boy from Delhi presents with intense pruritus and erythematous patches on his face, neck, and flexural surfaces (antecubital and popliteal fossae) for the past 8 months. His mother reports that symptoms worsen in winter and improve during monsoon. On examination, he has lichenification, excoriations, and a positive Dennie–Morgan fold. His serum IgE is elevated at 450 IU/mL. Skin prick testing shows reactivity to dust mites and pollen. What is the most appropriate first-line pharmacological management for acute flare control in this child?