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Acne vulgaris (acne) is the formation of comedones, papules, pustules, nodules, and/or cysts as a result of obstruction and inflammation of pilosebaceous units (hair follicles and their accompanying sebaceous gland). It most often affects adolescents. Diagnosis is by examination. Treatment is a variety of topical and systemic agents intended to reduce sebum production, infection, and inflammation and to normalize keratinization.

Pathophysiology

Acne occurs when pilosebaceous units become obstructed with plugs of sebum and desquamated keratinocytes, then colonized and sometimes infected with the normal skin anaerobe Propionibacterium acnes. Manifestations differ depending on whether P. acnes stimulates inflammation in the follicle; acne can be noninflammatory or inflammatory.

Comedones, uninfected sebaceous plugs impacted within follicles, are the signature of noninflammatory acne. Comedones are termed open or closed depending on whether the follicle is dilated or closed at the skin surface. Inflammatory acne comprises papules, pustules, nodules, and cysts.

Papules appear when lipases from P. acnes metabolize triglycerides into free fatty acids (FFA), which irritate the follicular wall. Pustules occur when active P. acnes infection causes inflammation within the follicle. Nodules and cysts occur when rupture of follicles due to inflammation, physical manipulation, or harsh scrubbing releases FFAs, bacteria, and keratin into tissues, triggering soft-tissue inflammation.

Etiology

The most common trigger is puberty, when surges in androgen stimulate sebum production and hyperproliferation of keratinocytes. Other triggers include hormonal changes that occur with pregnancy or throughout the menstrual cycle; occlusive cosmetics, cleansing agents, and clothing; and humidity and sweating. Associations between acne exacerbation and diet (eg, chocolate), inadequate face washing, masturbation, and sex are unfounded. Some studies question an association with milk products. Acne may improve in summer months because of sunlight’s anti-inflammatory effects. Proposed associations between acne and hyperinsulinism require further investigation.

Symptoms and Signs

Cystic acne can be painful; other types cause no physical symptoms but can be a source of significant emotional distress. Lesion types frequently coexist at different stages.

Comedones appear as whiteheads or blackheads. Whiteheads (closed comedones) are flesh-colored or whitish palpable lesions 1 to 3 mm in diameter; blackheads (open comedones) are similar in appearance but with a dark center.

Papules and pustules are red lesions 2 to 5 mm in diameter. In both, the follicular epithelium becomes damaged with accumulation of neutrophils and then lymphocytes. When the epithelium ruptures, the comedone contents elicit an intense inflammatory reaction in the dermis. Relatively deep inflammation produces papules. Pustules are more superficial.

Nodules are larger, deeper, and more solid than papules. Such lesions resemble inflamed epidermoid cysts, although they lack true cystic structure.

Cysts are suppurative nodules. Rarely cysts become infected and form abscesses. Long-term cystic acne can cause scarring that manifests as tiny, deep pits (“icepick scars”), larger pits, shallow depressions, or areas of hypertrophic scar.

Acne conglobata is the most severe form of acne vulgaris, affecting men more than women. Patients have abscesses, draining sinuses, fistulated comedones, and keloidal and atrophic scars. The back and chest are severely involved. The arms, abdomen, buttocks, and even the scalp may be affected.

Acne fulminans is acute, febrile, ulcerative acne, characterized by the sudden appearance of confluent abscesses leading to hemorrhagic necrosis. Leukocytosis and joint pain and swelling may also be present.

Pyoderma faciale (also called rosacea fulminans) occurs suddenly on the midface of young women. It may be analogous to acne fulminans. The eruption consists of erythematous plaques and pustules, involving the chin, cheeks, and forehead.

Diagnosis

Diagnosis is by examination. Differential diagnosis includes rosacea (in which no comedones are seen), corticosteroid-induced acne (which lacks comedones and in which pustules are usually in the same stage of development), perioral dermatitis (usually with a more perioral and periorbital distribution), and acneiform drug eruptions. Acne severity is graded mild, moderate, or severe based on the number and type of lesions; a standardized system is outlined in Table 1: Acne and Related Disorders: Classification of Acne Severity.

Table 1

Classification of Acne Severity

Severity

Definition

Mild

< 20 comedones, or < 15 inflammatory lesions, or < 30 total lesions

Moderate

20 to 100 comedones, or 15 to 50 inflammatory lesions, or 30 to 125 total lesions

Severe

> 5 cysts, or total comedone count > 100, or total inflammatory lesion count > 50, or > 125 total lesions

Prognosis

Acne of any severity usually remits spontaneously by the early to mid-20s, but a substantial minority of patients, usually women, may have acne into their 40s; options for treatment may be limited because of childbearing. Many adults occasionally develop mild, isolated acne lesions. Noninflammatory and mild inflammatory acne usually heals without scars. Moderate to severe inflammatory acne heals but often leaves scarring. Scarring is not only physical; acne may be a huge emotional stressor for adolescents who may withdraw, using the acne as an excuse to avoid difficult personal adjustments. Supportive counseling for patients and parents may be indicated in severe cases.

Treatment

Treatments (See also the Agency for Healthcare Quality’s summary of evidence report on management of acne) are directed at reducing sebum production, comedone formation, inflammation, and infection (see Fig. 1: Acne and Related Disorders: How various drugs work in treating acne.). Selection of treatment is generally based on severity; options are summarized in Table 2: Acne and Related Disorders: Drugs Used to Treat Acne. Affected areas should be cleansed daily, but extra washing, use of antibacterial soaps, and scrubbing confer no added benefit. Changes in diet are also unnecessary and ineffective, although moderation of milk intake might be considered for treatment-resistant adolescent acne. Peeling agents such as sulfur, salicylic acid Some Trade Names MEDIPLAST PROPA PH STRI-DEXClick for Drug Monograph , and resorcinol are minor therapeutic adjuncts.

Fig. 1

How various drugs work in treating acne.

Treatment should involve educating the patient and tailoring the plan to one that is realistic for the patient. Treatment failure can frequently be attributed to lack of adherence to the plan and also to lack of follow-up. Consultation with a specialist may be necessary.

Table 2

Drugs Used to Treat Acne

This table is presented as a PDF and requires the free Adobe PDF reader. Get Adobe Reader

Mild acne: Single-agent therapy is generally sufficient for comedonal acne; papulopustular acne generally requires dual therapy (eg, the combination of tretinoin Some Trade Names RETIN-AClick for Drug Monograph with benzoyl peroxide Some Trade Names BENZAC AC BENZAGEL NEUTROGENA ACNE MASKClick for Drug Monograph or topical antibiotics). Treatment should be continued for 6 wk or until lesions respond. Maintenance treatment may be necessary to maintain control.

A mainstay of treatment for comedones is daily topical tretinoin Some Trade Names RETIN-AClick for Drug Monograph as tolerated. Daily adapalene Some Trade Names DIFFERINClick for Drug Monograph gel, tazarotene Some Trade Names AVAGE TAZORACClick for Drug Monograph cream or gel, azelaic acid Some Trade Names AZELEX FINACEAClick for Drug Monograph cream, and glycolic or salicylic acid Some Trade Names MEDIPLAST PROPA PH STRI-DEXClick for Drug Monograph in propylene glycol are alternatives for patients who cannot tolerate topical tretinoin Some Trade Names RETIN-AClick for Drug Monograph . Adverse effects include erythema, burning, stinging, and peeling. Adapalene Some Trade Names DIFFERINClick for Drug Monograph and tazarotene Some Trade Names AVAGE TAZORACClick for Drug Monograph are retinoids; like tretinoin Some Trade Names RETIN-AClick for Drug Monograph , they tend to be somewhat irritating and photosensitizing. Azelaic acid Some Trade Names AZELEX FINACEAClick for Drug Monograph has comedolytic and antibacterial properties by an unrelated mechanism and may be synergistic with retinoids.

Mild inflammatory acne should be treated with topical benzoyl peroxide Some Trade Names BENZAC AC BENZAGEL NEUTROGENA ACNE MASKClick for Drug Monograph , topical antibiotics (eg, erythromycin Some Trade Names ERY-TAB ERYTHROCINClick for Drug Monograph , clindamycin Some Trade Names CLEOCINClick for Drug Monograph ), and/or glycolic acid. Combination preparations of these agents may help limit development of resistance. None have significant adverse effects other than drying and irritation (and rare allergic reactions to benzoyl peroxide Some Trade Names BENZAC AC BENZAGEL NEUTROGENA ACNE MASKClick for Drug Monograph ). Topical retinoids are often used concomitantly.

Physical extraction of comedones using a comedone extractor is an option for patients unresponsive to topical treatment. Comedone extraction may be done by a physician, nurse, or physician assistant. One end of the comedone extractor is like a blade or bayonet that punctures the closed comedone. The other end exerts pressure to extract the comedone.

Oral antibiotics (eg, tetracycline Some Trade Names ACHROMYCIN V TETRACYN TETREXClick for Drug Monograph , minocycline Some Trade Names MINOCINClick for Drug Monograph , doxycycline Some Trade Names PERIOSTAT VIBRAMYCINClick for Drug Monograph , erythromycin Some Trade Names ERY-TAB ERYTHROCINClick for Drug Monograph ) can be used when wide distribution of lesions makes topical therapy impractical.

Moderate acne: Moderate acne responds best to oral systemic therapy with antibiotics. Antibiotics effective for acne include tetracycline Some Trade Names ACHROMYCIN V TETRACYN TETREXClick for Drug Monograph , minocycline Some Trade Names MINOCINClick for Drug Monograph , erythromycin Some Trade Names ERY-TAB ERYTHROCINClick for Drug Monograph , and doxycycline Some Trade Names PERIOSTAT VIBRAMYCINClick for Drug Monograph . Full benefit takes ? 12 wk. Topical therapy as for mild acne is usually used concomitantly with oral antibiotics.

Tetracycline Some Trade Names ACHROMYCIN V TETRACYN TETREXClick for Drug Monograph is usually a good first choice: 250 or 500 mg bid (between meals and at bedtime) for 4 wk or until lesions respond, after which it may be reduced to the lowest effective dose. Rarely, dosage must be increased to 500 mg qid. After control is achieved, it is reasonable to attempt to taper and discontinue the oral antibiotic and continue topical therapy for control. Because relapse often follows short-term treatment, therapy may need to be continued for months to years, although for maintenance tetracycline Some Trade Names ACHROMYCIN V TETRACYN TETREXClick for Drug Monograph 250 or 500 mg once/day is often sufficient. Minocycline Some Trade Names MINOCINClick for Drug Monograph 50 or 100 mg bid causes fewer GI adverse effects, is easier to take, and is less likely to cause photosensitization, but it is the most costly option. Erythromycin Some Trade Names ERY-TAB ERYTHROCINClick for Drug Monograph and doxycycline Some Trade Names PERIOSTAT VIBRAMYCINClick for Drug Monograph are considered 2nd-line agents because both can cause GI adverse effects, and doxycycline Some Trade Names PERIOSTAT VIBRAMYCINClick for Drug Monograph is a frequent photosensitizer. Subantimicrobial doses of doxycycline Some Trade Names PERIOSTAT VIBRAMYCINClick for Drug Monograph have also been proven effective for acne and rosacea.

Long-term use of antibiotics may produce a gram-negative pustular folliculitis around the nose and in the center of the face. This uncommon superinfection may be difficult to clear and is best treated with oral isotretinoin Some Trade Names ACCUTANEClick for Drug Monograph after discontinuing the oral antibiotic. Ampicillin Some Trade Names OMNIPEN PRINCIPENClick for Drug Monograph is an alternative treatment for gram-negative folliculitis. In women, prolonged antibiotic use can cause candidal vaginitis; if local and systemic therapy does not eradicate this problem, antibiotic therapy for acne must be stopped.

Severe acne: Oral isotretinoin Some Trade Names ACCUTANEClick for Drug Monograph is the best treatment for patients with moderate acne in whom antibiotics are unsuccessful and for those with severe inflammatory acne. Dosage of isotretinoin Some Trade Names ACCUTANEClick for Drug Monograph is usually 1 mg/kg once/day for 16 to 20 wk, but the dosage may be increased to 2 mg/kg once/day. If adverse effects make this dosage intolerable, it may be reduced to 0.5 mg/kg once/day. After therapy, acne may continue to improve. Most patients do not require a 2nd course of treatment; when needed, it should be resumed only after the drug has been stopped for 4 mo. Retreatment is required more often if the initial dosage is low (0.5 mg/kg). With this dosage (which is very popular in Europe), fewer adverse effects occur, but prolonged therapy is usually required.

Isotretinoin Some Trade Names ACCUTANEClick for Drug Monograph is nearly always effective, but use is limited by adverse effects, including dryness of conjunctivae and mucosae of the genitals, chapped lips, arthralgias, depression, elevated lipids, and the risk of birth defects if treatment occurs during pregnancy. Hydration with water followed by petrolatum application usually alleviates mucosal and cutaneous dryness. Arthralgias (mostly of large joints or the lower back) occur in about 15% of patients. Increased risk for depression and suicide is much publicized but probably rare. CBC, liver function, and fasting glucose, triglyceride, and cholesterol levels should be determined before treatment. Each should be reassessed at 4 wk and, unless abnormalities are noted, need not be repeated until the end of treatment. Triglycerides rarely increase to a level at which the drug should be stopped. Liver function is seldom affected. Because isotretinoin Some Trade Names ACCUTANEClick for Drug Monograph is teratogenic, women of childbearing age are urged to use 2 methods of contraception for 1 mo before treatment, during treatment, and at least 1 mo after stopping treatment. Pregnancy tests should be done before beginning therapy and monthly until 1 mo after therapy stops.

Intralesional injection of 0.1 mL triamcinolone Some Trade Names ARISTOCORT KENACORT KENALOG NASACORTClick for Drug Monograph acetonide suspension 2.5 mg/mL (the 10 mg/mL suspension must be diluted) is indicated for patients with firm (cystic) acne who seek quick clinical improvement and to reduce scarring. Local atrophy may occur but is usually transient. For isolated, very boggy lesions, incision and drainage are often beneficial but may result in residual scarring.

Other forms of acne: Pyoderma faciale is treated with oral corticosteroids and isotretinoin Some Trade Names ACCUTANEClick for Drug Monograph . Acne fulminans is treated with oral corticosteroids and systemic antibiotics. Acne conglobata is treated with oral isotretinoin Some Trade Names ACCUTANEClick for Drug Monograph if systemic antibiotics fail. For acne with endocrine abnormalities, antiandrogens are indicated. Spironolactone Some Trade Names ALDACTONEClick for Drug Monograph , which has some antiandrogen effects, is sometimes prescribed to treat acne at a dose of 50 to 100 mg once/day. Cyproterone Some Trade Names No US trade nameClick for Drug Monograph acetate is used in Europe. When other measures fail, an estrogen-progesterone–containing contraceptive may be tried; therapy ? 6 mo is needed to evaluate effect.

Scarring: Small scars can be treated with chemical peels, laser resurfacing, or dermabrasion. Deeper, discrete scars can be excised. Wide, shallow depressions can be treated with subcision or collagen injection. Collagen implants are temporary and must be repeated every few years.

Last full review/revision August 2008 by Karen McCoy, MD, MPH

Content last modified August 2008

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