Acne is caused by a buildup of dead skin cells, bacteria, and dried sebum that blocks the hair follicles in the skin.
Bumps, such as blackheads, whiteheads, pimples, cysts, and sometimes abscesses, form on the skin, usually on the face, chest, shoulders, or back.
To diagnose acne, doctors examine the skin.
Common treatments include antibiotics and preparations applied to the skin for mild acne, antibiotics taken by mouth for moderate acne, and isotretinoin taken by mouth for severe acne.
Acne is the most common skin disease in the United States and affects 80% of the population at some point in life.
Causes of Acne
Acne is caused by an interaction between hormones, skin oils, and bacteria, which results in inflammation of hair follicles (the pores in the skin where hair grows). Acne is characterized by many types of skin abnormalities (lesions). They vary in size and severity, and some go deeper into the skin than others do:
Blackheads (open comedones)
Whiteheads (closed comedones)
Pimples (inflamed closed comedones)
Raised, solid bumps (papules)
Surface bumps containing pus (pustules)
Deeper, firm bumps containing pus (nodules)
Larger pockets containing pus (cysts)
Sometimes even larger, deeper pockets containing pus (abscesses)
Both cysts and abscesses are pus-filled pockets, but abscesses are somewhat larger and deeper.
Sebaceous glands, which secrete an oily substance (sebum), lie in the dermis, the middle layer of skin. These glands are attached to the hair follicles. Sebum, along with dead skin cells, passes up from the sebaceous gland and hair follicle and out to the surface of the skin through the pores.
Acne results when a collection of dried sebum, dead skin cells, and bacteria clogs the hair follicles, blocking the sebum from leaving through the pores.
A blackhead (open comedone) develops if the blockage is incomplete.
A whitehead (closed comedone) develops if the blockage is complete.
A pimple is an inflamed whitehead. The blocked sebum-filled hair follicle promotes overgrowth of the bacterium Cutibacterium acnes (formerly called Propionibacterium acnes), which is normally present in the hair follicle. This bacterium breaks down the sebum into substances that irritate the skin. The resulting inflammation causes the skin bumps that are commonly known as acne pimples. Deeper inflammation causes cysts and sometimes an abscess.
The most common trigger of acne is
Acne occurs mainly during puberty, when the sebaceous glands are stimulated by increased hormone levels, especially the androgens (such as testosterone), resulting in excessive sebum production. By a person's early to mid 20s, hormone levels usually have decreased enough that acne lessens or disappears. However, up to 40% of women may have acne into their 40s.
Other conditions that involve hormonal changes can affect the occurrence of acne as well:
Pregnancy or menstruation
Polycystic ovary syndrome
Certain products applied to the skin
High humidity and sweating
Acne may occur with each menstrual period in younger women and may clear up or substantially worsen during pregnancy. Polycystic ovary syndrome Polycystic Ovary Syndrome (PCOS) Polycystic ovary syndrome is characterized by slight obesity, irregular or no menstrual periods, and symptoms caused by high levels of male hormones (androgens). It involves disruption of the... read more (PCOS) is a hormone disorder that can disrupt the menstrual cycle and can trigger or worsen acne. The use of certain drugs, particularly corticosteroids and anabolic steroids Anabolic Steroids Anabolic steroids are synthetic (man-made) versions of testosterone that are used to increase muscle size. Anabolic steroids are hormones that promote muscle growth and increase strength and... read more , can worsen acne or cause acne flare-ups. Certain cosmetics, cleansers, and lotions may worsen acne by clogging the pores. Clothing that is too tight and high humidity and sweating can trigger acne.
Because acne naturally varies in severity for most people—sometimes worsening, sometimes improving—pinpointing the factors that may cause an outbreak is difficult. Acne is often worse in the winter and better in the summer, perhaps because of sunlight's anti-inflammatory effects. There is no relationship, however, between acne and inadequate face washing, masturbation, and sexual activity. It is not clear whether milk products, especially skim milk products, and a diet that is high in simple or processed carbohydrates and sugars (a high-glycemic diet Glycemic index Carbohydrates, proteins, and fats are the main types of macronutrients in food (nutrients that are required daily in large quantities). They supply 90% of the dry weight of the diet and 100%... read more ) contribute to acne.
Did You Know...
Symptoms of Acne
Most acne occurs on the face but is also common on the neck, shoulders, back, and upper chest. Anabolic steroid use typically causes acne on the shoulders and upper back.
There are three levels of acne severity:
Yet even mild acne can be distressing, especially to adolescents, who see each pimple as a major cosmetic challenge.
Comparing Mild Acne and Severe Acne
People with mild acne develop only a few noninflamed blackheads or whiteheads, or a moderate number of small, mildly irritated pimples. Pustules, which resemble pimples with yellow tops, may also develop. Blackheads appear as small flesh-colored bumps with a dark center. Whiteheads have a similar appearance but lack the dark center. Pimples are mildly uncomfortable and have a white center surrounded by a small area of reddened skin.
People with moderate acne have more blackheads, whiteheads, pimples, and pustules.
People with severe acne have either very large numbers of blackheads and whiteheads, pimples, and pustules or cystic (deep) acne. In cystic acne, people have cysts that are large, red, painful, pus-filled nodules that may merge under the skin into larger, oozing abscesses.
Mild acne usually does not leave scars. However, squeezing pimples or trying to open them in other ways increases inflammation and the depth of injury to the skin, making scarring more likely. The cysts and abscesses of severe acne often rupture and, after healing, typically leave scars. Scars may be tiny, deep holes (icepick scars); wider pits of varying depth; or large, irregular indentations. Acne scars last a lifetime and, for some people, are cosmetically significant and a source of emotional stress. Scars may be dark.
Acne conglobata is the most severe form of acne, causing severe scars and other complications resulting from abscesses. Severe acne can appear on the arms, abdomen, buttocks, and even the scalp.
Acne fulminans and pyoderma faciale (also called rosacea fulminans) are two possibly related and rare types of severe acne that typically occur suddenly.
Diagnosis of Acne
Examination of the skin
Doctors base the diagnosis of acne on an examination of the skin. Doctors look for certain symptoms, such as blackheads or whiteheads, to determine that the person has acne and not another skin disorder, such as rosacea Rosacea Rosacea is a persistent skin disorder that causes redness, tiny pimples, and noticeable blood vessels, usually on the central area of the face. The cause is unknown. Typical symptoms include... read more .
After the diagnosis is confirmed, doctors grade the severity of the acne as mild, moderate, or severe based on the number and type of lesions.
Prognosis of Acne
Acne of any severity usually lessens spontaneously by the early to mid 20s, but some people, usually women, have acne into their 40s. Some adults develop mild, occasional, single acne lesions.
Mild acne usually heals without scars. Moderate to severe acne heals but often leaves scars.
Acne can cause much emotional stress for adolescents and trigger social withdrawal. Counseling may sometimes be needed.
Treatment of Acne
For whiteheads and blackheads, tretinoin cream and/or benzoyl peroxide
For mild acne, skin treatment with tretinoin cream, sometimes with benzoyl peroxide or an antibiotic, or both
For moderate acne, antibiotics by mouth in combination with skin treatment as for mild acne
For severe acne, isotretinoin by mouth
For cystic acne, injected corticosteroids
General care of acne is very simple. Affected areas should be gently washed once or twice a day with a mild soap. Antibacterial or abrasive soaps, alcohol pads, and heavy frequent scrubbing provide no added benefit and may further irritate the skin.
Cosmetics should be water-based because very oily products can worsen acne.
A healthy, balanced diet should be followed (see under Nutritional Requirements Nutritional Requirements General guidelines for a healthy diet have been developed even though daily nutritional requirements, including those for essential nutrients, vary depending on age, sex, height, weight, physical... read more ). A diet that is low in simple or processed carbohydrates and sugars (a low-glycemic index diet Glycemic index Carbohydrates, proteins, and fats are the main types of macronutrients in food (nutrients that are required daily in large quantities). They supply 90% of the dry weight of the diet and 100%... read more ) and moderation of skim milk intake might be considered if treatment for acne is ineffective in adolescents.
Did You Know...
Some acne treatments are useful for specific people. For example, oral contraceptives may be given to women who have acne. This treatment takes more than 6 months to produce results. Spironolactone (a drug that blocks the action of the hormone aldosterone) also may help some women. Various therapies that use light have helped people who have inflammation (with pimples or pustules).
Acne treatment depends on the severity of the condition. Mild acne requires the simplest treatment that poses the fewest risks of side effects. More severe acne or acne that does not respond to preliminary treatment requires additional treatment. A treatment plan should always include education, support, and the most practical option for the person. People may need to see a specialist.
Drugs used to treat mild acne are applied to the skin (topical drugs). They work by either killing bacteria (antibiotics) or drying up or unclogging the pores (comedolytics). Older nonprescription creams that contain salicylic acid, resorcinol, or sulfur may help by drying out the pimples and causing slight peeling.
The most common prescription topical drug for blackheads and whiteheads is tretinoin. Tretinoin is very effective but is irritating to the skin and makes it more sensitive to sunlight. Doctors therefore use this drug cautiously, starting with infrequent applications and low concentrations, which can both be gradually increased. People who cannot tolerate tretinoin are given topical adapalene, azelaic acid, and glycolic or salicylic acid.
People who also have inflammation (with pimples or pustules) are given tretinoin combined with benzoyl peroxide, a topical antibiotic, or both. The two most commonly prescribed topical antibiotics are clindamycin and erythromycin. Minocycline foam and dapsone are other topical antibiotics. Topical antibiotics should not be used except when taken in combination with a retinoid, such as tretinoin, or benzoyl peroxide. Benzoyl peroxide is available with or without a prescription. Glycolic acid may be used instead of or in addition to tretinoin but is no longer commonly used.
Blackheads and whiteheads can be removed (called extraction) by a doctor, using instruments called comedone extractors and sterile needles.
Antibiotics taken by mouth (such as doxycycline, minocycline, tetracycline, and erythromycin) can be given to people who have more extensive acne than is manageable with topical drugs alone.
Moderate acne is usually treated with antibiotics given by mouth (orally). Typical antibiotics include doxycycline, minocycline, tetracycline, and sarecycline. Azithromycin, erythromycin, and trimethoprim/sulfamethoxazole are other options. People often use a topical treatment as for mild acne and an oral antibiotic. People may need to take antibiotics for about 12 weeks to achieve the maximum benefits.
If possible, oral antibiotics are stopped and topical treatments alone are used to maintain control. Because acne can recur after short-term treatment, therapy may need to be continued for months to years.
Women who take antibiotics for a long time sometimes develop vaginal yeast infections that may require treatment.
Women who are not helped by oral antibiotics may be given oral contraceptives, spironolactone, or both.
For the most severe acne, when antibiotics do not work, oral isotretinoin is the best treatment. Isotretinoin, which is related to the topical drug tretinoin, is the only drug that can potentially cure acne. However, isotretinoin can have very serious side effects. Isotretinoin can harm a developing fetus, and women taking it must use at least two forms of contraception before, during, and after treatment so they do not become pregnant. Other, less serious side effects may occur as well.
Therapy typically continues for 16 to 20 weeks but sometimes more.
Doctors give people with acne conglobata oral antibiotics. If antibiotics do not help, doctors give oral isotretinoin and corticosteroids.
Doctors give people with acne fulminans oral corticosteroids and antibiotics.
Doctors sometimes treat people with large, inflamed nodules or abscesses by injecting corticosteroids into them. Occasionally, a doctor cuts open a nodule or abscess to drain it.
Treatment of severe acne scars depends on their shape, depth, and location.
Multiple, small, shallow scars may be treated with chemical peels, laser treatments Using Lasers to Treat Skin Problems Port-wine stains are flat pink, red, or purplish discolorations present at birth due to malformed blood vessels. (See also Overview of Skin Growths and Overview of Growths and Malformations... read more , dermabrasion, and/or a newer treatment called microneedling. In microneedling, a small needle is injected, causing changes in the skin's collagen.
Dermabrasion is a procedure in which the skin surface is rubbed with an abrasive metal instrument to remove the top layer.
Individual shallow or deep scars may be cut out and the skin sewn back together.
Wide, indented scars can be improved cosmetically in a procedure called subcision, in which small cuts are made under the skin to release the scar tissue. This procedure often allows the skin to resume its normal contours.
Sometimes scars are injected with various substances such as collagen, fat, or a variety of synthetic materials. These substances may raise the scarred area to make it level with the rest of the skin. Fillers such as collagen, hyaluronic acid, and polymethylmethacrylate injections are temporary and must be repeated periodically. Some of the other injections are permanent.