Acne is a very common disorder in which the pores of the skin become blocked, resulting in inflammation and infection with the collection of pus. The sebaceous glands lie in hair follicles just below the surface of the skin in a layer called the dermis . These glands secrete oil through pores or on to the surface of the skin. During puberty the sebaceous glands become more active, probably due to changes in hormones. If the blockage is only partial, then a blackhead forms, whereas if the blockage is total, a whitehead forms.
Bacteria grow inside the blocked pore and breakdown the oil causing inflammation.
These irritated blackheads and whiteheads produce eruptions known as acne pimples. As the irritation and infection gets worse, pus collects and an abscess can result. Superficial acne is when a person has blackheads, whiteheads, pimples and pustules containing pus. If the pustules project deeper and rupture into the underlying skin, then the condition is called deep acne. The sun has a beneficial effect on skin with acne and therefore the condition tends to be worse in the winter and improve during the sunny summer months.