When the sun is strong like it has been recently I get a very lumpy very itchy rash on my hands (knees, neck and feet too if they're exposed) I went to the Dr as a child and she said it was an allergy to the sun rays. I've never really questioned it but do wonder if anyone else get's this and if it is an accurate diagnosis. It's definately not prickly heat which my step mother gets and is quite different. The rash I get has much bigger bumps!
I try and use suncream but if I put it on once the rash has developed it is a nightmare and gets very inflamed and even more itchy. I also find that once I've got it, it doesn't really disappear unless we have a prolonged period without any sun.