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Last Updated: Mar 1, 2019


Acne is a skin disorder that causes a variety of blemishes on the skin, including blackheads, whiteheads, pimples, nodules, and cysts.

Each hair on the human body grows upward through the skin and exits through a tiny opening called a follicle, or pore. The follicles also secrete sebum, an oil that acts as the skin’s natural “moisturizer.” Sebum is created by tiny glands within the skin that empty directly into the follicles.

Acne begins when hair follicles become clogged with excess sebum, dead skin cells and/or bacteria. Bumps develop on the skin surface as these waste products build up in the clogged follicle. In some cases, the blemish becomes infected, causing redness and tenderness.

Acne can affect any part of the skin but is most common in areas with lots of oil glands like the face, chest, back, neck, upper arms, shoulders and buttocks.

Left untreated, acne can cause significant scarring, especially if deeper cysts and nodules are present. As the blemishes heal, they may leave behind a discolored patch that lingers for months or years. Chronic (long-term) acne can also cause significant emotional distress, including low self-esteem and depression.

Acne is the most common skin disorder in the United States, affecting some 80 percent of preteens and teenagers. It also appears to be impacting more and more adults, though the reasons for this increase aren’t clear. Women are more likely than men to suffer from acne, as are people with a family history of the condition.

labeled illustration of skin cross-section showing follicle and sebaceous gland


Any condition that causes the skin to produce excess oil can trigger an outbreak of acne. Oil not only clogs pores, but also causes dead skin cells within those pores to stick together and makes them more difficult for the skin to excrete. The clogged pores create a favorable environment for certain bacteria that naturally live on the skin.

Possible acne triggers include:


Acne causes several kinds of skin blemishes.

Comedones are slightly raised, skin-colored bumps around the opening of a hair follicle. The trapped sebum inside may be open to the air (a blackhead) or closed (a whitehead). Comedones are considered a mild form of acne and aren’t likely to leave scars.

When bacteria invades a clogged follicle, it can cause redness, swelling, and pain. These “inflammatory” blemishes are more likely to cause scarring or discoloration. Types include:

Diagnosis and Treatment

Mild acne can often be treated at home using over-the-counter remedies containing benzoyl peroxide, salicylic acid, and similar chemicals. These treatments come in many forms, including creams, gels, cleansers, pads and sprays. They may cause mild skin irritation at first, which should go away after a few days of use. It’s often necessary to use an acne product for up to eight weeks before seeing an improvement.

Moderate and severe acne is usually treated by a skin specialist called a dermatologist, who can examine the blemishes and recommend a course of treatment. This often involves a combination of the following:

For large cysts that don’t respond to other treatments, a drug called isotretinoin may be prescribed. This treatment reduces the size of the oil glands and is very effective, resulting in permanent improvement in about 85 percent of people with severe acne. However, it is also riskier because it can cause potentially severe side effects, including liver problems and severe depression. Due to the risk to the fetus, women must avoid becoming pregnant during and immediately after treatment. Therapy usually lasts 4-5 months. Patients should follow up regularly with their dermatologists during this time.

While taking acne medication, you may notice some mild skin irritation, which should go away after a few days of use. You may also need to avoid the sun and tanning beds, because many medications make your skin more sensitive to UV radiation (the invisible energy waves that cause tanning and sunburn).

Some skin treatments are used in conjunction with medication therapy to control acne and treat scarring:

The good news is that almost every case of acne can be effectively managed, though the benefits of treatment may take 4-8 weeks to appear. Some people may need to continue treatment long-term to prevent new outbreaks. Many people who experience acne as preteens and teens eventually “grow out” of the condition.


To help prevent acne outbreaks:


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Tina Shahian, PhD

Tina is a writer for Innerbody Research, where she has written a large body of informative guides about health conditions.


A communication specialist in life science and biotech subjects, Tina’s successful career is rooted in her ability to convey complex scientific topics to diverse audiences. Tina earned her PhD in Biochemistry from the University of California, San Francisco and her BS degree in Cell Biology from U.C. Davis. Tina Shahian’s Linkedin profile.


In her spare time, Tina enjoys drawing science-related cartoons.