Acne Vulgaris

(Acne)

ByJonette E. Keri, MD, PhD, University of Miami, Miller School of Medicine
Reviewed/Revised Mar 2024
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Acne vulgaris 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). Acne develops on the face and upper trunk. It most often affects adolescents. Diagnosis is by examination. Treatment, based on severity, can involve a variety of topical and systemic agents directed at reducing sebum production, comedone formation, inflammation, and bacterial counts and at normalizing keratinization.

Acne is the most common skin disease in the United States and affects at least 70% of the population at some point in life (1).

General reference

  1. 1. Collier CN, Harper JC, Cafardi JA, et al: The prevalence of acne in adults 20 years and older. J Am Acad Dermatol 58(1):56-59, 2008. doi: 10.1016/j.jaad.2007.06.045

Pathophysiology of Acne Vulgaris

Acne occurs through the interplay of 4 major factors:

  • Excess sebum production

  • Follicular plugging with sebum and keratinocytes

  • Colonization of follicles by Cutibacterium acnes (formerly Propionibacterium acnes), a normal human anaerobe

  • Release of multiple inflammatory mediators

Acne can be classified as

  • Noninflammatory: Characterized by comedones

  • Inflammatory: Characterized by papules, pustules, nodules, and cysts

Noninflammatory acne

Comedones are sebaceous plugs impacted within follicles. They are termed open or closed depending on whether the follicle is dilated or closed at the skin surface. Plugs are easily extruded from open comedones but are more difficult to remove from closed comedones. Closed comedones are the precursor lesions to inflammatory acne.

Inflammatory acne

Papules and pustules occur when C. acnes colonizes the closed comedones, breaking down sebum into free fatty acids that irritate the follicular epithelium and eliciting an inflammatory response by neutrophils and then lymphocytes, which further disrupts the epithelium. The inflamed follicle ruptures into the dermis (sometimes precipitated by physical manipulation or harsh scrubbing), where the comedone contents elicit a further local inflammatory reaction, producing papules. If the inflammation is intense, grossly purulent pustules occur.

Nodules and cysts are other manifestations of inflammatory acne. Nodules are deeper lesions that may involve > 1 contiguous follicle, and cysts are large fluctuant nodules.

Etiology of Acne Vulgaris

The most common trigger is

  • Puberty

During puberty, surges in androgens stimulate sebum production and hyperproliferation of keratinocytes.

Other triggers include

  • Hormonal changes that occur with pregnancy or the menstrual cycle

  • Occlusive cosmetics, cleansers, lotions, and clothing

  • High humidity and sweating

Associations between acne exacerbations and inadequate face washing, masturbation, eating chocolate, and sexual activity are unfounded. Some studies suggest a possible association with milk products (1) and high-glycemic load diets (2). Acne may abate in summer months because of sunlight’s anti-inflammatory effects. Proposed associations between acne and hyperinsulinism (3, 4

Etiology references

  1. 1. Adebamowo CA, Spiegelman D, Berkey CS, et al: Milk consumption and acne in teenaged boys. J Am Acad Dermatol 58(5):787-793, 2008. doi: 10.1016/j.jaad.2007.08.049

  2. 2. Smith RN, Mann NJ, Braue A, et al: The effect of a high-protein, low glycemic-load diet versus a conventional, high glycemic-load diet on biochemical parameters associated with acne vulgaris: A randomized, investigator-masked, controlled trial. J Am Acad Dermatol 57(2):247-256, 2007. doi: 10.1016/j.jaad.2007.01.046

  3. 3. Vora S, Ovhal A, Jerajani H, et alBr J Dermatol 159(4):990-991, 2008. doi: 10.1111/j.1365-2133.2008.08764.x

  4. 4. Nagpal M, De D, Handa S, et alJAMA Dermatol 152(4):399-404, 2016. doi: 10.1001/jamadermatol.2015.4499

Symptoms and Signs of Acne Vulgaris

Skin lesions and scarring can be a source of significant emotional distress. Nodules and cysts can be painful. 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.

Manifestations of Acne
Acne With Large Comedones
Acne With Large Comedones

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Acne With Auricular Comedones
Acne With Auricular Comedones

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Skin Lesion (Pustule)
Skin Lesion (Pustule)

Pustules are elevated, usually yellow-topped lesions that contain pus. Scattered pustules appear on the face of this person with acne.

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Photo provided by Thomas Habif, MD.

Acne (Papules and Pustules)
Acne (Papules and Pustules)

Acne most commonly manifests as comedones (whiteheads or blackheads) and also as papules (blue arrow) and pustules (black arrow).

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Photo provided by Thomas Habif, MD.

Acne With Multiple Pustules
Acne With Multiple Pustules

Papules and crusts are also visible.

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Acne Affecting the Body
Acne Affecting the Body

Papules and comedones are present.

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Inflammatory Acne With Hyperpigmentation
Inflammatory Acne With Hyperpigmentation

Erythematous pustules and papules along with postinflammatory hyperpigmentation and scarring are present on the face.

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Papules and pustules are erythematous lesions 2 to 5 mm in diameter. Papules are relatively deep. 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 form deep abscesses. Long-term cystic acne can cause scarring that manifests as tiny and deep pits (icepick scars), larger pits, shallow depressions, or hypertrophic scarring or keloids.

Hyperpigmentation may result after inflammatory acne lesions resolve.

Acne With Abscess Formation
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Cystic Acne
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This photo shows suppurative nodules consistent with cystic acne.
Photo courtesy of Karen McKoy, MD.

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 Conglobata (Conglobate Acne) on the Face
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This photo shows acne conglobata, the most severe form of acne vulgaris, on the face. Abscesses and keloidal scars are visible.
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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.

Acne Fulminans
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This photo shows confluent and nonconfluent ulcerations resulting from acne fulminans.
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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. Papules and nodules may develop and become confluent.

Pyoderma Faciale (Rosacea Fulminans)
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This photo shows pyoderma faciale with erythematous plaques, papules, pustules, and confluent nodules.
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Pyoderma Faciale (Pregnancy-Related)
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This photo shows pyoderma faciale with erythematous plaques, papules, and pustules that occurred during pregnancy.
Photo courtesy of Karen McKoy, MD.

Diagnosis of Acne Vulgaris

  • Assessment for contributing factors (eg, hormonal, mechanical, or drug-related)

  • Determination of severity (mild, moderate, severe)

  • Assessment of psychosocial impact

Diagnosis of acne vulgaris 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 (see table Types of Drug Reactions and Typical Causative Agents). Acne severity is graded mild, moderate, or severe based on the number and type of lesions; one example of a standardized system is outlined in table Classification of Acne Severity.

Table
Table

Treatment of Acne Vulgaris

  • Moderate acne: Oral antibiotic plus topical therapy as for mild acne

It is important to treat acne to reduce the extent of disease, scarring, and psychological distress.

Treatment of acne involves a variety of topical and systemic agents directed at reducing sebum production, comedone formation, inflammation, and bacterial counts and at normalizing keratinization (see figure How Various Medications Work in Treating Acne ). Selection of treatment is generally based on severity; options are summarized in table Medications Used to Treat Acne. (See also the 2024 guidelines of care for the management of acne vulgaris from the American Academy of Dermatology.)

Affected areas should be cleansed once or twice a day, but extra washing, use of antibacterial soaps, and scrubbing confer no added benefit.

A lower-glycemic diet and moderation of milk intake might be considered for treatment-resistant adolescent acne, but the effectiveness of these measures in treating acne remains controversial (1).

Combined (estrogen plus a progestin) oral contraceptives are effective in treating inflammatory and noninflammatory acne (23, 4).

Various light therapies, with and without topical photosensitizers, have been used effectively, mostly for inflammatory acne, but supporting evidence is not high quality (5).

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.

How Various Medications Work in Treating Acne

Table
Table

Mild acne

Treatment of mild acne should be continued for 6 to 12 weeks or until lesions respond. Maintenance treatment is usually necessary to maintain control.

Single-agent therapy

Dual therapy

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

7).

Moderate acne

Oral systemic therapy with antibiotics 12 weeks.

Topical therapy as for mild acne is usually used concomitantly with oral antibiotics.

Long-term use of antibiotics may cause a gram-negative pustular folliculitiscandidal vaginitis; if local and systemic therapy does not eradicate this problem, antibiotic therapy for acne must be stopped.

Severe acne

Many patients do not require a second course of treatment; when needed, it is resumed only after the medication has been stopped for 4 (a few) months, except in severe cases when it may be resumed earlier. 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. Cumulative dosing has gained support; a total dosage of 120 to 150 mg/kg resulted in lower recurrence rates, and some experts suggest a higher cumulative dose of 220 mg/kg (8).

9).

Cystic acne

Other forms of acne

Acne fulminans is commonly treated with oral corticosteroids and systemic antibiotics.

6 months 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 injection of collagen or another filler. Fillers, including collagen, hyaluronic acid, and polymethylmethacrylate, are temporary and must be repeated periodically.

Treatment references

  1. 1. Dall'Oglio F, Nasca M, Fiorentini F, Micali G: Diet and acne: Review of the evidence from 2009 to 2020. Int J Dermatol 60(6):672–685, 2021. doi: 10.1111/ijd.15390 

  2. 2. Koltun W, Maloney JM, Marr J, et al:Eur J Obstet Gynecol Reprod Biol 2011 Apr;155(2):171-5. doi: 10.1016/j.ejogrb.2010.12.027. Epub 2011 Feb 2.

  3. 3. Grandhi R, Alikhan ADermatology 233(2-3):141-144, 2017. doi: 10.1159/000471799

  4. 4. Roberts EE, Nowsheen S, Davis MDP, et alJ Eur Acad Dermatol Venereol 34(9):2106-2110, 2020. doi: 10.1111/jdv.16302

  5. 5. Barbaric J, Abbott R, Posadzki P, et al: Light therapies for acne. Cochrane Database Syst Rev 9(9):CD007917, 2016. doi: 10.1002/14651858.CD007917.pub2

  6. 6. Bienenfeld A, Nagler AR, Orlow SJ: Oral antibacterial therapy for acne vulgaris: An evidence-based review. Am J Clin Dermatol 18(4):469–490, 2017. doi: 10.1007/s40257-017-0267-z

  7. 7. Hebert A, Thiboutot D, Stein Gold L, et alJAMA Dermatol 156(6):621–630, 2020. doi:10.1001/jamadermatol.2020.0465

  8. 8. Blasiak RC, Stamey CR, Burkhart CN, et al: High-dose isotretinoin treatment and the rate of retrial, relapse, and adverse effects in patients with acne vulgaris. JAMA Dermatol 149(12):1392–1398, 2013. doi: 10.1001/jamadermatol.2013.6746

  9. 9. Lee SY, Jamal MM, Nguyen ET, et alEur J Gastroenterol Hepatol 28(2):210–216, 2016. doi: 10.1097/MEG.0000000000000496

Prognosis for Acne Vulgaris

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.

Key Points

  • If noninflammatory, acne is characterized by comedones and, if inflammatory, by papules, pustules, nodules, and cysts.

  • Mild and moderate acne usually heals without scarring by the mid 20s.

  • Recommend that patients avoid triggers (eg, occlusive cosmetics and clothing, cleansers, lotions, high humidity, some medications, chemicals, possibly a high intake of milk products or a high-glycemic diet).

  • Consider the psychological as well as the physical effects of acne.

More Information

The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.

  1. American Academy of Dermatology: Guidelines of Care for the Management of Acne Vulgaris (2024)

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