Dry scaly patches on dog's skin?

Depending on the age and history of your dog, hair-loss can be caused by a number of things. Young dogs often get demodectic mange. It is a genetic condition that requires speedy treatment. Sarcoptic mange is another possibility. Sarcoptic mange is highly contagious to other dogs, and to humans and also requires speedy treatment. Both types of mange will cause secondary skin infections and can lower your dog's immune system leaving him prone to illness. Treatment requires a trip to the vet, so please do not try any of the old fashioned wives tale treatments as they can hurt your dog!

It is also possible that the hair loss is caused by something other than a parasite such as poor nutrition, some type of skin infection, Allergies, or stress. Regardless, a trip to the vet is in order.