My son, 12, always gets a rash in his inner elbow after a blood draw. he s about 163 cm, 67 kilo. healthy. this week he needed an ifusion for some medical procedure and told them about the rash in advance. They didn t think there was anything they could do differently and went ahead with the process. All was fine, no signs, until several hours later. Then he go the usual rash. In addition You could actually see the red line forming under his skin, where the plastic sleeve had been in his vein. Is this a n allergic reaction? topical antihistamine didn t help. It usually goes away after a week or so, but bothers him a lot. do we need to do something about this?