Acne typically appears on your face, neck, chest, back and shoulders. These areas of skin have the most oil (sebaceous) glands. Acne occurs when hair follicles become plugged with oil and dead skin cells.
Hair follicles are connected to oil glands. These glands secrete an oily substance (sebum) to lubricate your hair and skin. Sebum normally travels along the hair shafts and through the openings of the hair follicles onto the surface of your skin.
When your body produces an excess amount of sebum and dead skin cells, the two can build up in the hair follicles. They form a soft plug, creating an environment where bacteria can thrive. If the clogged pore becomes infected with bacteria, inflammation results.
The plugged pore may cause the follicle wall to bulge and produce a whitehead. Or the plug may be open to the surface and may darken, causing a blackhead. A blackhead may look like dirt stuck in pores. But actually the pore is congested with bacteria and oil, which turns brown when it's exposed to the air.
Pimples are raised red spots with a white center that develop when blocked hair follicles become inflamed or infected. Blockages and inflammation that develop deep inside hair follicles produce cyst-like lumps beneath the surface of your skin. Other pores in your skin, which are the openings of the sweat glands, aren't usually involved in acne.
Factors that may worsen acne
These factors can trigger or aggravate an existing case of acne:
Hormones. Androgens are hormones that increase in boys and girls during puberty and cause the sebaceous glands to enlarge and make more sebum. Hormonal changes related to pregnancy and the use of oral contraceptives also can affect sebum production. And low amounts of androgens circulate in the blood of women and can worsen acne.
Certain medications. Drugs containing corticosteroids, androgens or lithium can worsen acne.
Diet. Studies indicate that certain dietary factors, including dairy products and carbohydrate-rich foods — such as bread, bagels and chips — may trigger acne. Chocolate has long been suspected of making acne worse. A recent study of 14 men with acne showed that eating chocolate was related to an increase in acne. Further study is needed to examine why this happens or whether acne patients need to follow specific dietary restrictions.
Stress. Stress can make acne worse.
These factors have little effect on acne:
Greasy foods. Eating greasy food has little to no effect on acne. Though working in a greasy area, such as a kitchen with fry vats, does because the oil can stick to the skin and block the hair follicles. This further irritates the skin or promotes acne.
Dirty skin. Acne isn't caused by dirt. In fact, scrubbing the skin too hard or cleansing with harsh soaps or chemicals irritates the skin and can make acne worse. Though it does help to gently remove oil, dead skin and other substances.
Cosmetics. Cosmetics don't necessarily worsen acne, especially if you use oil-free makeup that doesn't clog pores (noncomedogenics) and remove makeup regularly. Nonoily cosmetics don't interfere with the effectiveness of acne drugs.