We've had 2 occassions when a couple of fleas attached themselves to one of our dogs. I phoned my homeopathic pet supplier and she recommended DE (diatomaceous earth)
We already had some food grade DE since it's useful for parasite control (a little mixed with food or in the water)
We rubbed (massaged) the DE powder into the fur all over, left it on for 3 days and after that brushed him out and then gave him a bath. Also, after vaccuming the house, we sprinkled a little DE around the furniture and bedding.
If fleas are a common problem, do the above once month. DE won't hurt but will actually help cats and dogs.
Here's some extra info on DE: http://wolfcreekranch1.tripod.com/defaq.html
And if I can add to this..........
If he's not on a raw diet, you may consider transitioning him to one. This will strengthen his immune system, making him not quite attractive to those fleas. Also, you may notice a vast improvement in his health.
One more thing......... Collidal silver in his water daily will go a long way with many health conditions. Dogs really respond to colloidal silver and you may notice him regaining the disposition he once had as a puppy.