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yes, wash and dry well.
I know talcum powder isn't recommended these days but I found it a great help when ds had this problem.
I think I've heard someone say you can use cornflour instead, but I might be making that up
It gets red because it gets sweaty and rubs. My babies used to get it in the neck folds, and under the armpits. I always washed gently with tepid water on a soft flannel, patted it to dry, and then rub in some Talcum powder with my finger tips. Works a treat.