Hi, I started getting this years ago and while the anti-histamines and WH etc can help with the itching the only thing that ever prevents it is a sun cream with a high UVA screen. Even if you buy one with a high factor it might not necessarily have a high UVA rating. There are several on the market and they usually say they are for skin with allergy to sunlight. I use a Piz Buin one and I bought a Simple one for DS which seems really good. I used a tiny bit on my arms today and obviously forgot to put more on as I have developed heat rash but only where the sun cream didn't reach!
Hope this helps - and as for the tan, gotta be fake I'm afraid!