i am thinking you most definately will need something stronger than flea shampoo to break the cycle. there is no such thing as a small case of fleas. believe me....one today, 5 million tomorrow. GL w. that. If it were me... i would be off to the VET and getting their recommended brand and dose.
I went through a flea takeover just recently all bc of a few fleas and an aging dog. Since he is aging, 17 yrs old, i did not want to unnecessarily medicate. I tried all natural methods, organic, spray on, and flea shampoo and collar. the d@mn things nearly took over the house...even AFTER all those treatments... so i went back to the vet and got their recommended stuff. expensive yes, but no more fleas, thank gosh.