Dawn...it works wonders for killing the little baby biters!!
Lather them up and let it sit for several minutes, rinse well and then I followed up with shampoo/conditioner.
I've used it when I suspected they might have fleas and if the do, you will see the little buggers jump off. Start at the top of the neck to create a barrier because the fleas will flee to the head to get away from the Dawn.