Black wetness on skin between paw pads.

My 6 months old cat has a kind of wetness (black staff) on the skin between the paw pads, inicially was only in his front left paw but now it is also in the back paws
I saw here older posts about it, with pictures that looked like the thing my cat has, but they do not tell if the cats are ok or what happened
If someone has a answer, please let me know. Thanks

He should see a vet.

Of course I took him to the vet, but they do not seem to know what is it, I just wanted a third opinion, or to know if other cats have recovered from it