How can I stop my dogs from pulling out their fur?

My family has three dogs. A large black german shephard who has sight problems, a very old britany spanial and a 2 year old shih tzu.The two larger dogs spend most of their time out side and the shih tzu is about 50/50 (inside/outside) They all eat the same type dogfood, stay in the same yard and use the same shampoo and flee and tick prevention. My problem is the to larger outside dogs are constantly pulling the fur off their backs and we have no idea why. We suspected thats flees were the problem so we changed their flee prevention and shampoo and even sprayed the entire 5 acre lot with flee spray. That did nothing. Then we read that it could be caused by poor nutrition causing the skin to dry out and itch so we bought a higher grade dog food and that also did nothing.What has us so baffled is that it has only effected the two larger dogs, not the shih tzu. We do know that the dogs' skin is extremly dry. What are some other options to soothe the dry skin and help their coats?

How can I stop my dogs from pulling out their fur?
It could be a number of reasons. One of the more probable reasons would be allergies. You can ask the vet for antihistamines or if those don't work you could try allergy testing.





Also, with the flea treament -- if you are using a topical treatment, such as Advantage or Frontline, you do not need to use a flea shampoo. And, you shouldn't give a bath two days before or two days after applying the treatment.





I agree, you should bring them into the vet.








****In response to the answer below me -- it is not recommended to use human shampoo on animals. They are often too harsh and dry out the pet's skin and make it worse. If you must, you can use diluted baby shampoo but make sure to rinse very well. Also, only bathe as little as you have to. Once a month at most. Frequent bathing also dries out the skin and can make their skin condition worse.****
Reply:oh i think you should get them to the vet, just to make sure its not mange or something else. You love your animals, they are worth it. Call now.
Reply:I don't know if brushing your dog's hair is normal routine, but that activity stimulates their folicles while at the same time removing any loose tufty hair that will shed out.
Reply:I think the two larger dogs (who spend more time outside playing) might be dehydrated to some degree. Rehydration will add the moisture back into their skin. Yip, Yip !
Reply:the same thing happens to my dogs... the hair comes and goes right? it could be the weather or dehydration that dies up the skin. you could try special treated shampoo for dry skin or take him to the vet
Reply:i think you should go tell a vet.i recommend regular peoples' shampoo.it works on my dog but don't try it if you beleive it is too severe.maybe it is the tick prevention, shampoo, dogfood, or the yard (where they eat in)that is causing it.