Firstly - you need to make sure that your dog is definitely up to date with flea control. Make sure you are using a flea product appropriate for her weight. Even though 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 girl'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).Bascially dogs are allergic to four main things - food, fleas, grasses/plants (contact allergy) or environmental allergens (canine atopy - the dog version of ezcema). I am sure you have worked through all of these with your Veterinarian, but 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 3 - 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 Hill's Z/D ultra allergen free and needs to be fed SOLELY for 3 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. 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.
It is also possible your dog may 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. Sarcoptic mange has been ruled out by your Vet, but you really need to check they have ruled out the other mites and lice that can effect canine patients! There could well be something else going on here such as Demodectic mange which is a little harder to spot and requires on going treatment. 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.
You really should get your girl checked out by a different Vet to get a second opinion if your first Vet really cannot come up with a diagnosis. If it is that hard to work out what is going on here, a skin biopsy would be the next best step. You should also purchase a medicated shampoo that will deal with both yeast and bacteria and as above, Malaseb is the most ideally suited for this. This 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.
Best of luck with your girl and I hope this has been of help to you. Please reply if you need any more information on this.
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Kind Regards,
Dr M D Edwards
Dog Veterinarian
Veterinarian - BVSc (DVM equivalent) - Webmaster & Head Veterinarian for www. onlinepetdr.com