I agree, get the bloodwork done now.
Demodectic mange is usually only a problem when the dog has a suppressed immune system. Make sure he is on a good diet, and if he has pustules he'll need an oral antibiotic as well as a topical anti parasitic cream. Also you can try bathing him every couple days, or once a week depending on the severity, in a shampoo with benzoyl peroxide.
__________________ Kellie  and  Morgan |