The appearance of black things like blackheads in the hair follicles of dogs may be caused by insect eggs, fungal infection, folliculitis, etc. In severe cases, hair loss, itching, redness, swelling, and ulceration may occur. When abnormalities are found on the dog, You must take your dog to the pet hospital for examination and treatment in time, adjust the dog's diet, try to feed lighter food, bathe the dog regularly and deworm it to avoid bacterial infection.