To my knowledge, no one has ever gotten sick from eating these cookies, despite leaving eggs and butter dough out on the counter overnight. I have no idea if the ammonium carbonate needs this time to work; this is just how we have always made them. At any rate, do NOT eat this cookie dough while it is raw.You can substitute 1/4 teaspoon baking powder plus 1/4 teaspoon baking soda for the ammonium carbonate with good results, per my sister.