fleas and frontline (not working)

[nmarlow]

I have 5 dogs, 3 outside & 2 inside. They have always been on frontline
for flea prevention. It's not working anymore. I don't mind the cost as
long as it works. Someone told me that the fleas have build up a resistance
& I need to change products. I even used a dip from the vet. The fleas were

back on the next day. HELP.....Any suggestions??

[GermanShepherds]

Wow. I have 6 outside dogs. I use Frontline on all of them. It works on my 4 six and seven month old pups. But on my 2 four year old dogs it doesnt work. Im wondering if the bigger the dog, the more you need. Bathing with Seargents Flea and Tick shampoo works great on the Bog Boys.