I have been getting red itchy bumps that turn into large grapelike blisters on my body. This happens only in the summer . The blisters look just like the pics of spider bite blisters that are shown on the internet but I have never seen a bug on me.My doc says that they are not bites but a reaction to something. After the blister breaks a dark area remains and looks like a cigarette burn.They appear 2 or 3 at a time and are intensely itchy. IT is driving me crazy. My five year old granddaughter has the same problem and her pediatrician says it's a reaction to mosquito bites but noone has ever seen a bug biting her either. Please help..