The medical term for a blackhead is a comedo. Comedones are usually caused by a poor diet consisting of high glycemic foods: sugar, refined starches, soda, and scant animal protein and fat. They are the precursor to acne; in fact, pimples cannot form in the absence of comedones. In older people, comedones can form around the eyes on prematurely aged skin.
Treatment with topical retinoid cream for 2 months can clear these unsightly lesions so see your dermatologist.