Hello, thanks for your question today! I am Dr. Drew, and I am a licensed veterinarian. I'll be happy to help you in any way I can.
certainly, Demodectic Mange is a possible explanation for patchy hair loss in a young puppy,
a skin scraping is easily performed by a veterinarian, to check for this condition.
there's no way to diagnose this without a skin scraping.
Other possible causes include bacterial infection and/or yeast infection.
Ringworm (fungal infection) also is possible.
so if the skin scraping is negative (no mites), then some tests need to be done for those other issues.
At-home care, without a diagnosis, would have to consist of antimicrobial shampoo twice a week, such as one containing Chlorhexidine or Benzoyl peroxide.
If there is no improvement within 7-10 days, then veterinary care is surely a requirement.