Causes
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a "whitehead"
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pimples can lead to significant swelling and may appear on the back and chest
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Blackheads -- sebum darkened by contact and reaction with air
Inside the pore are sebaceous glands which produce sebum. When the outer layers of skin shed (as they do continuously), the dead skin cells left behind may become 'glued' together by the sebum. This causes the blockage in the pore, especially when the skin becomes thicker at puberty. The sebaceous glands produce more sebum which builds up behind the blockage, and this sebum harbours various bacteria including the species Propionibacterium acnes, causing infection and inflammation.
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