Licking/Scratching

Question
I have a 4 yr old Aussie he is wonderful with our animals and grandchildren, The only problem i have is he scratches all the time he is on a flee treatment every month.he has also chewed the hair off his top rear hind legs area,and chews at his front legs.We have tried shampoo's on him.I am not sure i would like to learn more about allergies and the Aussie's so I can maybe make some changes in my home to see if that helps.any info will be of great help. thank you.

Answer
This dog needs to see a vet.  There are many things that cause hair loss, and allergies are just one.  Hypothyroidism runs in this breed and can cause hair loss and anxiety.  One flea bite makes some dogs really itchy (flea bite dermatitis).  Some dogs have food allergies (common problem items: wheat, corn, soy, chicken).  The only way to tell is to get a proper diagnosis.  Don't wait until the situation is worse - it will cost you more in the long run.  
Here is a good article on food allergies: http://www.peteducation.com/article.cfm?c=2+2111&aid=143
Here's one on environmental allergies and atopy:
http://www.peteducation.com/article.cfm?c=2+2082&aid=503
And on hypothyroidism (I think all Aussies should be tested, although it doesn't sound like your dog is hypothyroid, as the hair just falls out, they usually don't chew on their skin)
http://www.peteducation.com/article.cfm?c=2+1597&aid=449
This is a GREAT article on itch problems! http://www.thepetcenter.com/gen/itch.html
Make sure your dog is on a good diet, too (and that doesn't mean the cheap stuff from the supermarket).  If you can, try a premium food (they generally cost the same to feed, because they are higher in k/Cal so you feed less).