The black dandruff you have noticed on your schnauzer's skin is not really dandruff. Regular canine dandruff caused by dry skin or allergies is white or flesh colored. The black debris in your schnauzer's coat is one of two things. The first option is that your dog has fleas and the black spots you are seeing are waste from the flea infestation. The other option is that your schnauzer is suffering from a breed specific disorder called schnauzer comedone syndrome that affects primarily miniature schnauzers. If your dog has comedone syndrome, it can be managed with proper veterinary care but not cured.
Put your schnauzer in the bathtub and give him a bath. Inspect his skin closely as you bathe him with a gentle dog shampoo. If the water you are washing your dog with is turning reddish brown or you see fleas moving around on your dog's skin, he has fleas and the black spots are likely flea dirt. Wash him in a flea shampoo and invest in flea treatment.
Finish washing your dog and examine his skin again. If the black spots stayed put throughout the bath, appear to be scabs or are accompanied by bumps on the skin, your dog probably has schnauzer comedone syndrome also known as comedo syndrome.
Take your schnauzer to the veterinarian to confirm the diagnosis. Comedone syndrome is an inherited condition also is known as schnauzer bumps. The condition causes blackheads to appear on your dog's skin. These black bumps are caused by hair follicles that get blocked when your dog's skin produces too much keratin and sebum. Sebum is the oily substance responsible for making your dog's skin and fur waterproof. The black bumps can be scabby and crusty and may look like black dandruff.
Follow your veterinarian's recommended treatment. Common methods of treating this condition include regular bathing and grooming to reduce oils on the skin, antibiotics and vitamin supplements. Some dogs have responded well to treatment with commercial and prescription acne medications.
Jen Davis has been writing since 2004. She has served as a newspaper reporter and her freelance articles have appeared in magazines such as "Horses Incorporated," "The Paisley Pony" and "Alabama Living." Davis earned her Bachelor of Arts in communication with a concentration in journalism from Berry College in Rome, Ga.