Can my dog get blackheads on their belly and how do I treat them?

Hello and thank you for reaching out to Petco Pet Education Center, formerly Petcoach. From what you are describing these sound like comedones, or clogged pores. A comedone is similar to a pimple, in that it is a collection of oily material in a pore. It is black because of exposure to oxygen and accumulation of debris. Comedones may be a sign of a skin issue such as mites, or over-secretion of oils, but they can also be signs of an underlying hormonal disease such as Cushing's disease. As long as they are not irritating to your dog, there is no need to try to get rid of them. Comedones may be reduced by use of benzoyl peroxide shampoos, which have “follicular flushing action,” the ability to go down inside pores and hair follicles and remove foreign material. I recommend contacting your regular veterinarian who may recommend a medicated shampoo, and/or may recommend that your dog be seen for an exam and bloodwork to evaluate for any underlying diseases that may be related to his/her comedones. I hope this is helpful!