Well when I get sun burn I get an allergic reaction....
Can't remember the last time I had a real tan
Anyways, Aloe is either 100% awesome for you (it promotes skin healing) or its gonna make you itch like fuck.
Anyways, its red cause you destroyed the top layer of skin with radiation, so your body is pumping loads of blood there to fix it. The only way to reduce the actual redness is my applying ice packs, as it gently slows down the flow of blood into your capillaries at the skin surface.
When I was younger I got so bad I had to have a steroid injection in my butt haha