A 27 yr old boy has itchy, excoriated papules on the forehead and exposed pas of the arms and legs for 3 years. The disease was most severe in the rainy season and improved completely in winter. What is the most likely diagnosis?

In this case, diagnosis can be made by excluding each option. This patient is least likely to have scabies, as it does not produce lesions on the face in adults. Atopic dermatitis is unlikely since he is giving a history of similar lesions only since 3 years. In atopic dermatitis lesions first appears in infancy and then continues into childhood and adulthood. By this time lesions become more and more lichenified. Uicaria is characterised by the presence of evanescent wheals due to edema of dermis, and it last only for 24- 48 hours. So the most appropriate diagnosis would be insect bite hypersensitivity. In this condition the characteristic lesions are itchy persistent papules with a central punctum, seen mainly on exposed pas of the body and aggrevated during rainy season.