Ear discharge is an unusual substance or material coming from your dog’s ear. Often, the discharge’s specific color and smell will provide a clue as to the cause. Brown to black discharge with a foul odor is suggestive of a yeast infection. A foul smelling yellowish green pasty discharge is often the sign of a bacterial infection. Dark brown discharge that resembles coffee grinds is often a sign of ear mites. All cases of ear discharge need to be evaluated by your veterinarian.