Acne is a skin condition that occurs when your hair follicles become plugged with oil and dead skin cells. Acne usually appears on your face, neck, chest, back and shoulders. Effective treatments are available, but acne can be persistent. The pimples and bumps heal slowly, and when one begins to go away, others seem to crop up.

Acne is most common among teenagers, with a reported prevalence of 70 to 87 percent. Increasingly, younger children are getting acne as well.

Depending on its severity, acne can cause emotional distress and scar the skin. The earlier you start treatment, the lower your risk of lasting physical and emotional damage.

Acne signs and symptoms vary depending on the severity of your condition:

• Whiteheads (closed plugged pores)
• Blackheads (open plugged pores — the oil turns brown when it is exposed to air)
• Small red, tender bumps (papules)
• Pimples (pustules), which are papules with pus at their tips
• Large, solid, painful lumps beneath the surface of the skin (nodules)
• Painful, pus-filled lumps beneath the surface of the skin (cystic lesions)

When to see a doctor

If home care remedies don’t work to clear up your acne, see your primary care doctor. He or she can prescribe stronger medications. If acne persists or is severe, you may want to seek medical treatment from a doctor who specializes in the skin (dermatologist).

The Food and Drug Administration warns that some popular nonprescription acne lotions, cleansers and other skin products can cause a serious reaction. This type of reaction is quite rare, so don’t confuse it with the redness, irritation or itchiness where you’ve applied medications or products.

Seek emergency medical help if after using a nonprescription skin product you experience:

• Faintness
• Difficulty breathing
• Swelling of the eyes, face, lips or tongue
• Tightness of the throat

Four main factors cause acne:

• Oil production
• Dead skin cells
• Clogged pores
• Bacteria

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:

• 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.
• 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 can make acne worse.

Acne myths

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 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.

Risk factors for acne include:

• Hormonal changes. Such changes are common in teenagers, women and girls, and people using certain medications, including those containing corticosteroids, androgens or lithium.
• Family history. Genetics plays a role in acne. If both parents had acne, you’re likely to develop it, too.
• Greasy or oily substances. You may develop acne where your skin comes into contact with oily lotions and creams or with grease in a work area, such as a kitchen with fry vats.
• Friction or pressure on your skin. This can be caused by items such as telephones, cellphones, helmets, tight collars and backpacks.
• This doesn’t cause acne, but if you have acne already, stress may make it worse.