Tiny black dots?

Question
I have a dachshund-lab mix that I got from a shelter about a month & a half ago.

When I got him, he had 2 little bald spots - 1 right above his eye and another on the side of his torso.  Both spots were probably just slightly smaller than a quarter.

I took him to a vet and they did a skin scraping - he was negative for mites, and they did a fungal culture - negative for that.  In the meantime, while they were waiting for test results, they gave me a solution to put on him (supposed to cure a lot of things).  This solution cleared up the patch on his head (the bald spot is gone), but the one on the torso didn't change.

Recently I noticed that both locations have tiny black spots on them, almost like a blackhead or something.  He doesn't itch, and they don't seem to bother him, but I'm just confused as to what they are.

Answer
It is very hard to be specific on a lesion as you described without doing a complete skin examination. These could be blocked sebaceous glands causing comedones. They could be infections.  Or these could be something called acanthosis, which is common in Doxies and their mixes.  I can suggest that if normal treatments don't help, a skin biopsy can help your vet to know what the problem is.  If the problem is something that can be treated specifically, then the vet can help get to resolution faster than continuously trying new treatments that may or may not work.