Scabies lesions are papular or papulovesicular. Furrows are often found if they are sought in the palms and soles of the feet. The lesions break easily resulting in crusts. Large bullous lesions suggest a secondary bacterial infection.
Atopic dermatitis presents with dry, scaling skin. The response to local hydrocortisone and barrier creams is usually favourable.
Chickenpox is characterized by vesicles, fever, and a rapid course.
Urticaria, particularly dermographism, starts abruptly. In dermographism hives are not visible but they can be triggered by scratching the skin bluntly.
In children, infections easily trigger urticaria, which should be differentiated from pox diseases.
Hypersensitivity may present only with itch. Known causes include citrus fruit, fresh strawberries, and cocoa.
In the summer an itch may be a symptom of hypersensitivity to light.
Mastocytosis (urticaria pigmentosa) is a rare cause of an itch.