Simplified, oily skin is a product of internal stimulation and oil gland overactivity. Blackheads are dilated pores blocked with cell debris. Over the counter benzoyl peroxide washes and creams are very effective for decreasing oil on the skin. They must be used in the morning and usually mid day. Benzoyl peroxides also have an antibacterial effect and help decrease blackhead formation. The retinoids (retinol) are also very effective for blackheads. These products also help prevent blackhead formation. These products are best used at night.
The above products are used for daily maintenance. If you already have stubborn blackheads, a warm washcloth (5min) and comedone extractor (located at the drugstore) are helpful - once or twice a week. Finally, glycolic acid facial treatments once a week help clean and exfoliate the skin