I just found out the name for something I’ve seen in my son for a few years now. He has dermagraphia, also known as “skin writing”. If you lightly scratch or rub a spot on his skin, many times a dramatic welt will rise in that spot. It lasts about ten minutes or so, then fades away. It’s caused by cells in the surface of the skin releasing histamines, causing localized skin swelling.
It’s not harmful, but the poor little boy is always complaining about being itchy - and of course when he scratches the spot it just gets worse. Often after the swelling fades you’ll see little spots where his scratching has broken the skin.
It can be mildly alarming. If he has trouble tugging off a shirt that has a tight neck, for example, his face might be covered in welts for a while afterwards. We’ve had the school call us because he has turned up covered in welts after playing outside.
He’s already on Singulair for mild asthma, now we’re about to try Clarinex to see if that helps.