Sorry to hear your having a tough time with fleas in your area......in my opinion it is a bad idea to put flea treatments on your pet every two weeks. If your vet advises this I would switch also. Most vets are
very ignorant on the dangers of flea meds. A vet will tell you they are very safe, this is far from the truth. These treatments are very hard on the livers, thyroid and kidneys of your dogs. If you do choose to use them the pet must not be bathed 48 hours before applying it. It needs the oils on the skin to work properly. You also have to wait at least 24-48 hours after applying to bath so as to not wash off. Here's a link that might help with some natural alternatives...
Chinaroad Lowchens of Australia - Ticks, fleas, bees, flies, snakes and other gremlins! And how to deal with them!
I don't know if this will work, but here is a link about flea treatments and how they work....
http://www.apnm.org/publications/res...leachemfin.pdf
Good luck.....