Acne is a common skin condition causing pimples and other abnormalities on the face and upper torso.
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.
Acne is the most common skin disease in the United States and affects 70% 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, some women 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 medications
Certain products applied to the skin
Too-tight clothing
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 (PCOS) is a hormone disorder that can disrupt the menstrual cycle and can trigger or worsen acne. The use of certain medications, particularly corticosteroids and anabolic steroids, 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, eating chocolate, and sexual activity. It is not clear whether milk products and a diet that is high in simple or processed carbohydrates and sugars (a high-glycemic diet) contribute to acne.
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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 3 levels of acne severity:
Mild acne
Moderate acne
Severe acne
Yet even mild acne can be distressing, especially to adolescents, who may 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, cysts 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.
This photo shows dark acne scars.
© Springer Science+Business Media
Acne commonly causes whiteheads (arrow), blackheads, and pimples.
Photo provided by Thomas Habif, MD.
This photo shows large blackheads (open comedones) and whiteheads (closed comedones).
© Springer Science+Business Media
This photo shows blackheads (open comedones) in the ear.
© Springer Science+Business Media
© Springer Science+Business Media
This photo shows dark acne scars.
© Springer Science+Business Media
Acne commonly causes whiteheads (arrow), blackheads, and pimples.
Photo provided by Thomas Habif, MD.
This photo shows large blackheads (open comedones) and whiteheads (closed comedones).
© Springer Science+Business Media
This photo shows blackheads (open comedones) in the ear.
© Springer Science+Business Media
© Springer Science+Business Media
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 2 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.
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.
Treatment of Acne
For moderate acne, antibiotics by mouth in combination with skin treatment as for mild acne
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). A diet that is low in simple or processed carbohydrates and sugars (a low-glycemic index diet) and moderation of milk intake might be considered if treatment for acne is ineffective in adolescents, but the effectiveness of these measures in treating acne is controversial.
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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.
Mild acne
Blackheads and whiteheads can be removed (called extraction) by a doctor, using instruments called comedone extractors and sterile needles.
Moderate acne
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.
Severe acne
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 fulminans oral corticosteroids and antibiotics.
Medications Used to Treat Acne
Medication | Some Side Effects | Comments |
|---|---|---|
Kills bacteria (applied to the skin) | ||
Diarrhea (rarely) | Should be avoided in people with inflammatory bowel disease | |
Very rarely causes methemoglobinemia (a disorder that impairs the ability of the blood to carry oxygen) | ||
Rarely irritated skin | Well-tolerated Frequent development of bacterial resistance | |
Irritation, dry skin, redness | Foam propellant is flammable. Fire, flame, and smoking should be avoided immediately after application. | |
Dry skin Possible bleaching of clothing and hair Allergic reactions (rarely) | ||
Unclogs pores (applied to the skin) | ||
Irritated skin (with dryness, redness, and scaling) Sensitization of skin to sunlight | Requires use of protective clothing and sunscreen during sun exposure Should be avoided during pregnancy | |
Irritated skin Sensitization of skin to sunlight | Requires use of protective clothing and sunscreen during sun exposure Should be avoided during pregnancy | |
Some redness, burning Increased sun sensitivity | Requires use of protective clothing and sunscreen during sun exposure | |
May lighten skin | Minimally irritating Should be used cautiously in people with darker skin because of skin-lightening effects but can help lighten areas that darken skin after healing | |
Glycolic acid | Stinging Mild irritation | Over-the-counter product in form of a cream, lotion, or solution used in addition to prescription products but no longer commonly used |
Stinging Mild irritation | Over-the-counter product in form of a wash, peel, mask, or lotion used in addition to prescription products | |
Dryness, redness, and scaling of the skin Increased sun sensitivity | Requires use of protective clothing and sunscreen during sun exposure | |
Kills bacteria (taken by mouth) | ||
Sensitization of skin to sunlight | Inexpensive and safe, but must be taken on an empty stomach Requires use of protective clothing and sunscreen during sun exposure | |
Sensitization of skin to sunlight | Requires use of protective clothing and sunscreen during sun exposure | |
Headache Dizziness Skin discoloration | Most effective antibiotic according to some experts but is expensive | |
Stomach upset | ||
Stomach upset | ||
Sensitization of skin to sunlight Stomach upset Light-headedness, dizziness, or vertigo | Requires use of protective clothing and sunscreen during sun exposure | |
Stomach upset Rash | ||
Unclogs pores (taken by mouth) | ||
Possible harm to a developing fetus Possible effect on blood cells, the liver, and fat (triglyceride and cholesterol) levels Dry eyes, chapped lips, and drying of the mucous membranes Pain or stiffness of large joints and lower back with high dosages Unclear whether associated with new or worsened inflammatory bowel disease (Crohn disease and ulcerative colitis) | Requires blood tests to check whether the medication is affecting blood cells, the liver, or fat levels | |
Blocks action of hormones | ||
Redness, scaling or dryness, and itching | For treatment of acne in people 12 years of age and older | |
Combined (estrogen and progestin) contraceptives (taken by mouth) | High blood pressure (hypertension), blood clots, breakthrough vaginal bleeding (for example, between menstrual periods) Weight gain Stomach upset Headaches | For treatment of acne in females |
Light-headedness Increased urination Breast tenderness Stomach upset | For treatment of acne in females | |
Cystic acne
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.
Acne scars
Treatment of severe acne scars depends on their shape, depth, and location.
Multiple, small, shallow scars may be treated with chemical peels, laser treatments, dermabrasion, and/or microneedling. Dermabrasion is a procedure in which the skin surface is rubbed with an abrasive metal instrument to remove the top layer. Microneedling is a newer treatment in which small needles are used to prick the skin, causing changes in the skin's collagen.
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.
Prognosis for 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.
