Ever since I was 16 (now 23) when I get sun burned even the slightest little burn I have a rash that comes up on my left collar bone/ chest area its always in the same spot and it comes up about a week after i get burned. It shows up very fast and the blisters get very big. The rash is very painful. It itches and stings. I was first told it was sun poisoning and then i have a slight allergy to the sun and last year i was told its shingles. Does anyone know what this could be?????