This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Dermatitis, Subject name: Dental
A child scratches his hand with pen.A red wheal appears which persists for 30 minutes. What would be the diagnosis? 
Select and explain. 
A. Atopy, B. Contact uicaria, C. Pressure uicaria, D. Dermographism
D: Dermographism
Answer: D: Dermographism 
Explanation: Dermographism: type of physical uicaria induced by mechanical stimulus also called Skin writing rapid appearence of wheal flare at the site of brisk firm storke made with a firm objectLesions are often linear/ assume the shape of eliciting stimulus.Local erythema followed by edema.Most common physical uicaria seen in young adults sometimes symptomatic pruritus is present the onset of lesiona IADVL textbook of dermatology, cutaneous vascular responses, page 661