May I recommend using Brewers yeast for Flea control? It is the best option and healthy for the pet. You can get it at pet stores in a tablet or at your General Health food store in a powder. Try to avoid the ones with Garlic. Garlic causes bad smelling gas.
Brewers yeast works as a "Repellant". You can not smell it but the Brewer's yeast will secrete through the dogs hair follicles and the Fleas Hate the smell.
Not only is it good for Fleas but their Coats will be better and softer! It does take some time to work and make sure your dog doesn't have an allergy to Yeast.
I have a dog that is allergic to fleas and often flea killers are too harsh for him and me.
Try this solution. It can be cheaper buying the powder form at the Health food store and easier to apply.