Are you okay if you eat the pastries or cakes cold? When you say warm, do you mean fresh out of the oven?
I can't imagine what may cause the flare, but all I know is, when I was a child I was forbidden by my mother, to eat any cake, pastry or bread while it was warm and fresh out of the oven. She always told me it would upset my belly and give me indigestion!
I don't know why.