Dog with Allergy or Demodex?

[extreme_g_2]

Just this week my 11 mo. old Siberian Husky female started losing hair near the corner of her mouth. The hair loss is just on one side of her face. I took her to the vet and they originally diagnosed demodectic mites. This was confirmed with a skin scraping, however demodectic mites are present on ALL dogs in limited numbers. The only reason they would get out of control is if the dog has a weakened immune system. The skin scraping only produced two or three mites, one of which was dead. However, a day or two after our visit to the vet, she has been scratching at the bald area at night causing bleeding. Itching is usually not a symptom of demodex. Over the last couple weeks I have been noticing a large number of unripened tomatoes in my yard. The dog has been eating these tomatoes and grabbing them from a tomato plant bordering our fence. I ripped out the invasive plant yesterday. Could a tomato allergy cause the hair loss and itching? OR could it be the demodex or some other cause?