Thank you for your patience. While there are a number of things that could be causing Harley's itching, it is most likely that your girl has skin parasites or fungi, or possibly even an allergy with a secondary bacterial and/or yeast infection.
Firstly - you need to make sure you are using a flea product appropriate for Harley. Even if you cannot see any fleas on her doesn't mean there are one or two lurking and oftentimes this is all it takes for a dog with flea allergy dermatitis. In your girls's case it does sounds like she may have an underlying allergy of some sort with secondary infection, however this could also be caused by parasites or fungi (ringworm or yeast).
Basically dogs are allergic to four main things - food, fleas, grasses/plants (contact allergy) or environmental allergens (canine atopy - the dog version of ezcema). I always like to ensure I have talked through each of these with my clients here in New Zealand. Flea allergies are avoided by strict flea control - every 4 weeks with Advantage or Advantage Multi or every 5 - 6 weeks with Frontline. You must also ensure all dogs in the household are treated at the same time. For a food allergy, you need to undertake a food trial with a 'novel protein' diet such as Royal Canin Anallergenic or Hill's Z/D and needs to be fed SOLELY for 8 - 12 weeks. After this time if you are seeing a change in your dog's allergy you can slowly introduce different foods week by week with the guidance of your Veterinarian. If Harley has never had lamb before - then the lamb and rice food you are using could potentially be used as a novel protein, but check the ingredients list on the bag, as it may contain other proteins in it. The safest bet here is one of the diets mentioned above for this reason. Contact allergies are best treated by avoidance of the plants that are to blame, but identifying the exact cause of a contact allergy can be very hard. A referral to a canine skin specialist may be the way to go in Harley's case for either a skin patch test or a blood allergen test.
It is also possible that Harley could have skin mites or lice as they commonly cause intense itching and irritation. These could be either Demodex (less itchy) or Sarcoptes mites (VERY itchy) and you should ensure a full Veterinary check up so that he or she can carry out a physical examination and possibly a skin scrape to check for mites and lice, as well as signs of fleas. The next step would be to double check for fungal disease (such as ringworm) and there are several tests for this including a UV light and a fungal culture. It could also be that your dog has a bad yeast problem - and a good medicated shampoo such as Malaseb may well do the trick! Again a full Vet check will be able to confirm or deny this. If after these tests there is no diagnosis, the next step would be to carry out a food trial as above.
I really would encourage you to get your girl checked out at your Vet clinic as I am a little worried this could be mites or fleas. For the best thing for her in the mean time, as above, is a medicated shampoo that will deal with both yeast and bacteria - Malaseb (or a similar product containing both Chlorhexidine and Miconazole) is the most ideally suited for this. The Malaseb shampoo requires you to make a lather and leave this lather on for 10 minutes before washing off! For many clients this is easier said that done, but it is SO important. In the meantime, you may want to try a little Benadryl - the typical dose is 1mg per pound of body weight up to twice daily. You can read more about the use of Benadryl in dogs online here: http://www.petplace.com/article/drug-library/library/over-the-counter/diphenhydramine-benadryl .
I hope all of the above makes sense? If you have more questions or if I can help in any other way, please do not hesitate to ask! If you would like to accept my answer, please press RATE OUR CONVERSATION (I am not compensated in any other way). Bonuses are always welcome. Thanks! I hope to work with you again soon!
PS: If you have additional questions after you rate the question, you are welcome to request me for additional conversations if I am on-line or by beginning your question "Dr. E..." or "Pet-doc..." and others will leave the questions for me.