Ok, my dog is a long haired chihuahua and is almost a year old. He’s had fleas for a month or two maybe more. Everyday I swear he gets almost a billion new fleas. The flea shampoo we’re using is by Hartz. I just bathed him in it and it’s worse than ever. We’ve been trying to stay consistent with the shampoo using it once a week. I used it just about four days ago. And a weeek or two before that. The fleas are mainly on his belly and hide legs area. I think most of the fleas are coming from our backyard. But it’s strange he’s like infested with fleas and we have three cats and they seem just fine. We let them roam around the outside one of them lives outside. What would be the best possiblem least costly, and most effecient way to get rid of the fleas on our dog and in the backyard and keep them out?