I think my baby has heat rash and I feel so guilty! It was so cold on saturday night and she ketp waking up and her feet and legs were so cold so I pu her in a fleece sleep and play, but i guess that was too hot because two hours later when I went to wake her up, she had a rash all over her belly, neck, back and also on her face and arms. I'm assuming its heat rash. How long before it goes away?