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. Acne may worsen or improve during pregnancy. Diet is unlikely to affect acne, although many people find that eliminating certain foods can cause an improvement in the condition. The symptoms are usually obvious.