Dull complexion, uneven skin, white heads and black heads are actually signs of clogged and congested skin. White heads, black heads, and clogged pores occur due to a combination of factors, such as accumulated toxins and excess sebum (sometimes from over cleansing), pollution, dead skin cells, make-up and dirt. They can enter the open pores and combine with continuously producing sebum and oil causing a plug to form. Oil and Sebum Sebaceous glands are tiny, oil producing glands connected to hair follicles beneath the surface of the skin. The oil they produce lubricates skin and hair. The sebum moves up the hair follicle to the opening of the follicle. However,.