Mine have the same thing. I'm getting closer to the answers tho. Are yours still sick? Mine also have skin turned dark then with 40% sink cream many left. I'm not sure if it's fungal or parasite. Up close it looks like something fromma horror movie. I think what's in the hair that you've found might be pieces sloughed off. Do the ones you've found feel more gritty than sandpaper. Like metal shavings type feel at times? If your dogs sleep on you beware. I'm not sure if I have this but it's really likely. My other postings have details. The anemia and off and on receid of my gums expose a horable sight. I worry about not getting the issues to go away.
Does food left out get dark spots specks. Like even sour cream n cheddar chips get black specks fairly quickly no matter how I ziplock etc. It takes a few more days to get them with my only reaching in once a day to pull a handful out. This may not be related.
I get the same black stuff in between my toes and bottoms of feet if I place an air tight bag on them overnight.
I think I'm going to try the desitin and see if it works on myself also.
!!!!!!The dark skin is a layer of parasites!!!!
My boy's ballsack peeled off but initially got infected or swole up double in size. He may be sterile now..vet tried to blame desitin. They never acknowledged parasites. In fact said darkening skin was a normal life thing fir dogs. Well both my pugs have pink belly skin again. My boy's balls turned polkadotted then black again so I need to re treat.
Did you ever find what yours was as I've seen no ines replied to your post??
I'm not sure if it's the same thing but hair infiltrated by one of these parasites. Hard to explain. Message if interested in more of my experience k. I hope to hear back from you.