you need to go to the vet and get some anti itch tablets .. it sounds like its gone from *its fleas* to a flea allergy! do it while your dog has hair.. believe me they can rip their hair out in no time ..only takes a few days of being on the anti itch meds and our girl stops with the constant itching/licking herself bald and sore.
one bite from a flea is all it takes to send your dog on a endless mission to scratch an itch that is not there <== what my vet told me
the sad misery of it is you will probably have this bad reaction every summer as our girl and heaps of other dogs/cats do
as mentioned earlier in your thread most flea treatments work by killing the fleas after they have bitten ..one bite is all it takes to start that horrid itch cycle
yes invest in a hard floor hoover .. hehe took us years of buying regular good quality hoovers to realize they sit higher while hoovering as they are designed for carpets so spit junk out as they don't sit close enough to the floor when hoovering a hard floor
have comfort in winter and the colder weather will be here in no time.. then the fleas go into hybernation so the problem will ease