I've posted this before and use Dawn Dish Soap in the girls shampoo to prevent/kill fleas - READ this site for more information
http://my.homewithgod.com/mkcathy/household/animal.html
we have never had fleas but today my hubby THINKS he saw one...so far I haven't and checked the girls really good but I AM bathing them with Dawn today - this really works !!
then you can use a precsription medication -
but please NO HARTZ Products !!! That can kill a small dog