Are these common? I went to hold my cat today after work and noticed a foul oder coming from his ear and noticed it was full of some kind of nasty black puss. I don't understand why as he is an indoor cat. It is possible that when he was around the litter he got it. Hopefully its minor and the vet will have some kind of kitty friendly ear drops for him.
Those sound like earmites! Better get to the store for the Earmite drops. They can spread to humans although it dosen't happen that often. Get the bottle and read the directions and don't stop until the black is completly gone. It will spread to another cat if you have more than one.