Black particles attached to dog hair may be caused by fleas, mites, fungi, or dirt. You can put the black particles into the water. If the particles turn red, it is the feces of fleas or mites, and you need timely help. The dog undergoes external deworming; if it does not turn red, you need to bathe the dog and pay attention to the dog's hygiene. If the dog relapses later, you need to take the dog to the pet hospital for examination.