My child gets up with red itchy welts on her back , i get it to stop itching & it goes away, now she has it on her butt same thing red itchy welts. ?

Dermatographism: Dermatographism means the ability to write on the skin. People with this form of chronic urticaria are sensitive to touch and pressure, as well as scratching. The areas of skin that are touched or scratched get a raised, red and itchy rash. While many people with chronic urticaria have some features of dermatographism, people with true dermatographism have pressure as the only trigger.