I've just started my son on the milk ladder at 12 months. I gave him a step 1 cookie which has 1/40 of a teaspoon of baked milk powder in it and within 24 hours he got bad nappy rash. I've tried again twice since then and the same has happened both times. It must be a reaction to the cows milk but is it really possible to react to an amount this small? He was only diagnosed at 6 months and prior to that he was breastfed with me having plenty of cows milk and him not reacting...?