Thinning Hair and Firm Patches on One Foster Puppy's Face

A negative skin scraping doesn't fully rule out demodectic mange. Mites can be missed, especially on the face, and vets often repeat the test with a deeper scraping or by plucking hairs to look at under the microscope. Ringworm, a fungal infection, is another common cause of patchy hair loss in puppies, and it can affect just one puppy in a litter. A fungal culture or special lamp exam checks for it.

Firm, rough patches that keep spreading without itching are worth a recheck now rather than waiting. Ask your vet about repeat scrapings or hair plucks, a fungal culture, and whether a small skin biopsy would help if those are negative. A few uncommon puppy skin conditions are only diagnosed by biopsy.

Until you know it isn't ringworm, handle this pup with gloves or wash your hands well, and keep its bedding separate, since ringworm can spread to other animals and people.

See demodectic mange in puppies, ringworm on dogs and hair loss in dogs.

This is general information, not a diagnosis. Please follow your own vet's advice.