Heat Rash????

I'm a Malaysian girl... born in the sweltering heat.. grew up in the sweltering heat for so many years..
9 months in UK.....
come summer i am getting a heat rash.. i noticed it when i was taking a walk today.... btw.. today was really bright sunny and hot hot hot...
but a malaysian girl who never had a heat rash getting a heat rash after almost a year in UK.. is ridiculous... aaaaaaaaarghhhhhhhh...