There are a whole heap of other washing alternatives to store bought washing powders.
Have a look at some cloth nappy sites for these - they are very effective and designed for use with cloth nappies and for eco friendly folk, so rarely contain allergens or irritants .

check out the bum genius (australian - google it) website - they have some great washing powder made from mineral salts and plant materials.
There are also soap nuts etc...

You could also wander over to the Cloth Nappy Genreal Discussion thread and ask the girls what they use