One thing you might notice with your miniature schnauzer is something called Schnauzer Comedo Syndrome. From the top of the head, to the tip of the tail, along the middle of the back, you might see scabby bumps. Relax, this isn't a life threatening condition. And it's treatable, you get it under control, but since it's considered possibly genetic, you may occasionally find them re-occurring.
These comedones are simply just hair follicles that are blocked by an excess of skin oils and keratin, not much different from the blackheads that a human might suffer from.
Beware, though, never pick the scabs off, as they could cause a secondary infection, resulting in the need for antibiotics.
I have noticed, feeding a high quality dog food does help lessen the flareups.
Clip away the hair from infected skin on longhaired dogs (don’t clip shorthaired dogs), and bathe the dog twice a day for 10 days with a povidone-iodine shampoo such as Betadineor one with chlorhexidine such as Nolvasan. As the skin infection improves, switch to a benzoyl peroxide shampoo such as Stiff DermaBenss, Sebolux Oxyderm +PS or Pyoben, used once or twice a week. Continue until healing is complete.
Then others have recommended Fish oil added to their diet. Depending on the serverity, this can be treated....