Suggest Treatment For Allergy And Rashes All Over Body

Hello there, my daughter has had a problem with her skin since she was born.It seems when we are on holidays or when we get nice weather, she gets a rash all over her body which becomes red and inflammed and eventually turns into a bad case of eczma.I've tried lots of sun tan lotions but still the same thing happens.it's so uncomfortable for her and spoils every holiday we have.I took her to gp to do an allergy test but they said she was too young.I bought simple sun cream yesterday to do do an experiment of my own before the summer arrives and I have the same problem again.Just 4 hours after I applied the cream my daughter has been itching through the night in the creases of her legs,arms and neck.I now believe that it is definately the suncream,but I don't know which one to use as I 've tried so many??I feel so helpless.We go on holidays in May and I don't want her to go through all this again.Poor thing.I feel that I have to use suncream to give her some protection against exposure to the sun.