Fleas on newborns

My month-old babies have fleas.

I went against the back of the shampoo and bathed them, which seemed to work but apparently it hasn't. Should I just keep shampooing them? Has anyone used the Hartz tubes on newborns?

While we're on the topic: Advantage or Frontline? And where's the cheapest place to get it? (for the other four cats)

Several people have mentioned boric acid, where do I find that and is it better than flea powders sold for that purpose?

Please do not tell me you bathed your 1 month olds in Hartz flea shampoo? Please call you vet and tell them you did this. Most of Hartz products are toxic to newborns!

They cannot be de-flead with anything but a flea comb and some warm water with a few drops of Dawn dishwashing detergent until they are at least 6 weeks old.

I am completely serious that you may have inadvertently harmed these babies and there is a chance that they will die because of it.