Almost 90% of Asian men living in the tropics have excessively oily skin and clogged pores. Skin contains oil glands which produces sebum (oil) through the pores to moisturize the skin and the hair.
Excess sebum causes the pore to be adhesive to minute debris on the skin surface and clogs the pores. The sebum cannot exit the pore and this pore eventually fills with dead skin cells and bacteria. If it is a small hair follicle, a layer of skin forms over the top and it may be infected by bacteria to form a pimple. When this occurs in a larger hair follicle, the protective layer of skin is not able to form and the bacteria-filled pore is exposed to air.
The air causes oxidation and discoloration of the particles within the hair follicle and a blackhead is formed. Blackheads are also known as comedones.