Acne vulgaris

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This article is about a skin disease common during adolescence. For other acneform skin diseases, see Acne (disambiguation).
Acne vulgaris
Acne in a 14-year-old male during puberty
Classification and external resources
ICD-10 L70.0
ICD-9 706.1
DiseasesDB 10765
MedlinePlus 000873
eMedicine derm/2
Patient UK Acne vulgaris
MeSH D000152

Acne vulgaris (or simply acne) is a long term condition characterized by areas of blackheads, whiteheads, pimples, greasy skin, and possibly scarring.[1][2] Other effects may include anxiety, reduced self-esteem, and in extreme cases, depression or thoughts of suicide.[3][4]

Genetics is estimated to be the cause of 80% of cases.[2] The role of diet as a cause is unclear.[2] Neither cleanliness nor sunlight appear to be involved.[2] Acne mostly affects skin with a greater number of oil glands; including the face, upper part of the chest, and back.[5] During puberty in both sexes, acne is often brought on by an increase in androgens such as testosterone.[6]

Many different treatments exist. Eating fewer simple carbohydrates like sugar may help.[7] Medications for acne include topical benzoyl peroxide, salicylic acid, and azelaic acid among others.[8] Medications available both by mouth and topically include antibiotics and retinoids.[8] Resistance, however, may develop to antibiotics.[9] A number of birth control pills may be useful in women.[8] Oral isotretinoin is typically only used in cases of severe disease due to greater potential side effects.[8] Early and aggressive treatment is advocated by some to lessen the overall long-term impact to individuals.[10]

Acne occurs most commonly during adolescence, affecting an estimated 80–90% of teenagers in the Western world.[11][12][13] Lower rates are reported in some rural societies.[13][14] In 2010 it was estimated to be the 8th most common disease globally affecting 650 million people.[15] People may also be affected before and after puberty.[16] While rates decreases in adulthood, around half of people still have problems in their twenties and thirties.[2] About 4% continue to have difficulties into their forties.[2]

Signs and symptoms[edit]

Typical features of acne include seborrhea (increased oil-sebum secretion), microcomedones, comedones, papules, pustules, nodules (large papules), and possibly scarring.[1][17] The appearance of acne varies with skin color. It may result in psychological and social problems.[12]

Some of the large nodules were previously called cysts and the term nodulocystic has been used to describe severe cases of inflammatory acne.[18]


Acne scars are the result of inflammation within the dermal layer of skin brought on by acne and are estimated to affect 95% of people with acne vulgaris.[19] The scar is created by an abnormal form of healing following this dermal inflammation.[19] Scarring is most likely to occur with severe nodulocystic acne, but may occur with any form of acne vulgaris.[19] Acne scars are classified based on whether the abnormal healing response following dermal inflammation leads to excess collagen deposition or collagen loss at the site of the acne lesion.[19]

Atrophic acne scars are the most common type of acne scar and have lost collagen from this healing response.[19] Atrophic scars may be further classified as ice-pick scars, boxcar scars, and rolling scars.[19] Ice pick scars are typically described as narrow (less than 2 mm across), deep scars that extend into the dermis.[19] Rolling scars are wider than ice pick scars (4-5 mm across) and have a wave-like pattern of depth in the skin.[19] Boxcar scars are round or ovoid indented scars with sharp borders and vary in size from 1.5-4 mm across.[19]

Hypertrophic scars are less common and are characterized by increased collagen content after the abnormal healing response.[19] They are described as firm and raised from the skin.[19][20] Hypertrophic scars remain within the original margins of the wound whereas keloid scars can form scar tissue outside of these borders.[19] Keloid scars from acne usually occur in men and on the trunk of the body rather than the face.[19]


Postinflammatory hyper pigmentation (PIH) is usually the result of nodular or cystic acne (the painful 'bumps' lying under the skin). They often leave behind an inflamed red mark after the original acne lesion has resolved. PIH occurs more often in people with darker skin color.[21] Pigmented scar is a common but misleading term, as it suggests the color change is permanent. Often, PIH can be avoided by avoiding aggravation of the nodule or cyst. These scars can fade with time. However, untreated scars can last for months, years, or even be permanent if deeper layers of skin are affected.[22] Daily use of SPF 15 or higher sunscreen can minimize pigmentation associated with acne.[22]



Hormonal activity, such as menstrual cycles and puberty, may contribute to the formation of acne. During puberty, an increase in sex hormones called androgens cause the follicular glands to grow larger and make more sebum.[5][23] A similar increase in androgens occurs during pregnancy, also leading to increased sebum production.[24] Use of anabolic steroids may have a similar effect.[25] Several hormones have been linked to acne including the androgens testosterone, dihydrotestosterone (DHT) and dehydroepiandrosterone sulfate (DHEAS), as well as insulin-like growth factor 1 (IGF-I) and growth hormone.[26]

Late-onset acne vulgaris (developed after puberty) between the ages of 21 and 25 is uncommon.[27] True acne vulgaris in adult women may be a feature of an underlying condition such as pregnancy, or disorders such as polycystic ovary syndrome.[28] Menopause-associated acne (known as acne climacterica) occurs as production of the natural anti-acne ovarian hormones estradiol and progesterone fails, permitting the acnegenic hormone testosterone to exert its effects unopposed.


The predisposition for specific individuals to acne is likely explained by a genetic component, which has been supported by twin studies as well as studies that have looked at rates of acne among first degree relatives.[29] The genetics of acne susceptibility is likely polygenic, as the disease does not follow classic Mendelian inheritance pattern. There are multiple candidates for genes which are possibly related to acne, including polymorphisms in TNF-alpha, IL-1 alpha, and CYP1A1 among others.[11]


While the connection between acne and stress has been debated, scientific research indicates that increased acne severity is associated with increased stress levels.[30] The United States' National Institutes of Health list stress as a factor that can cause an acne flare.[31]


Propionibacterium acnes (P. acnes) is the anaerobic bacterium species that is widely suspected to contribute to the development of acne lesions, but its exact role in this process is not entirely clear.[29][32] Regardless, there are specific clonal sub-strains of P. acnes associated with normal skin health and others with long-term acne problems. It is as yet inconclusive whether any of these undesirable strains evolve on-site in the adverse conditions or are all pathogenically acquired, or possibly both depending on the individual patient. These strains either have the capability of changing, perpetuating, or adapting to, the abnormal cycle of inflammation, oil production, and inadequate sloughing activities of acne pores. At least one particularly virulent strain, though, has been circulating around Europe for at least 87 years.[33] In vitro, resistance of P. acnes to commonly used antibiotics has been increasing, as well.[34] Infection with the parasitic mite Demodex is associated with the development of acne.[17][35] However, it is unclear if eradication of these mites improves acne.[35]


The relationship between diet and acne is unclear as there is no good quality evidence.[36] However, a high glycemic load diet is associated with worsening acne.[7][37] There is weak evidence of a positive association between the consumption of milk and a greater rate and severity of acne.[35][38][39][40] Other associations such as chocolate and salt are not supported by the evidence.[38] Chocolate does contain a varying amount of sugar that can lead to a high glycemic load and it can be made with or without milk. There may be a relationship between acne and insulin metabolism and one trial found a relationship between acne and obesity.[41]


Acne develops as a result of blockages in the follicles. Hyperkeratinization and formation of a plug of keratin and sebum (a microcomedo) is the earliest change.[5] Sebaceous glands enlargement and an increase in sebum production occur with increased androgen (DHEA-S) production at adrenarche. The microcomedo may enlarge to form an open comedo (blackhead) or closed comedo. Comedones result from the clogging of sebaceous glands with sebum, a naturally occurring oil, and dead skin cells.[5] In these conditions, the naturally occurring largely commensal bacterium Propionibacterium acnes can cause inflammation within and around the follicle, leading to inflammatory lesions (papules, infected pustules, or nodules) in the dermis around the microcomedo or comedone, which results in redness and may result in scarring or hyperpigmentation.[5][42][43] Severe acne is inflammatory, but acne can also be noninflammatory.[27]


There are multiple scales for grading the severity of acne vulgaris,[44] three of these being:

  • Leeds acne grading technique: Counts and categorizes lesions into inflammatory and non-inflammatory (ranges from 0–10.0).
  • Cook's acne grading scale: Uses photographs to grade severity from 0 to 8 (0 being the least severe and 8 being the most severe).
  • Pillsbury scale: Simply classifies the severity of the acne from 1 (least severe) to 4 (most severe).

Differential diagnosis[edit]

Similar conditions include rosacea, folliculitis, keratosis pilaris, perioral dermatitis, and angiofibromas among others.[12]


Many different treatments exist for acne including benzoyl peroxide, antibiotics, retinoids, antiseborrheic medications, anti-androgen medications, hormonal treatments, salicylic acid, alpha hydroxy acid, azelaic acid, nicotinamide, and keratolytic soaps.[45] They are believed to work in at least four different ways, including the following: normalizing skin cell shedding and sebum production into the pore to prevent blockage, killing P. acnes, anti-inflammatory effects, and hormonal manipulation.[5]


Benzoyl peroxide[edit]

Benzoyl peroxide cream

Benzoyl peroxide is a first-line treatment for mild and moderate acne due to its effectiveness and mild side-effects (mainly irritant dermatitis). It works against P. acnes, helps prevent formation of comedones, and has anti-inflammatory properties.[5] Benzoyl peroxide normally causes dryness of the skin, slight redness, and occasional peeling when side effects occur.[46] This topical does increase sensitivity to the sun as indicated on the package, so sunscreen use is often advised during the treatment to prevent sunburn. Benzoyl peroxide has been found to be nearly as effective as antibiotics with all concentrations being equally effective.[46] Unlike antibiotics, benzoyl peroxide does not appear to generate bacterial resistance.[46] Benzoyl peroxide may be paired with a topical antibiotic or retinoid such as benzoyl peroxide/clindamycin and benzoyl peroxide/adapalene, respectively.[21]


Antibiotics are reserved for more severe cases and decrease acne due to their antimicrobial activity against P. acnes in conjunction with anti-inflammatory properties.[5][46] They are believed to work both by decreasing the number of bacterial and as an anti-inflammatory.[2] With increasing resistance of P. acnes worldwide, they are becoming less effective.[46] Commonly used antibiotics, either applied topically or taken orally, include erythromycin (category B), clindamycin (category B), metronidazole (category B), and tetracyclines such as doxycycline and minocycline.[24] Topical erythromycin and clindamycin are considered safe to use as acne treatment during pregnancy due to negligible systemic absorption.[24] Nadifloxacin and dapsone are other topical antibiotics that may be used to treat acne in pregnant women, but have received less extensive study.[24] It is recommended that oral antibiotics be stopped and topical retinoids be used once the disease has improved.[8]

Salicylic acid[edit]

Salicylic acid (category C)[24] lessens acne due to its bacteriostatic and keratolytic properties.[47] Additionally, salicylic acid can open obstructed skin pores and promotes shedding of epithelial skin cells.[47] Hyperpigmentation of the skin has been observed in individuals with darker skin types who use salicylic acid.[5]

Azelaic acid[edit]

Azelaic acid has been shown to be effective for mild-to-moderate acne when applied topically at a 20% concentration.[42] Application twice daily for six months is necessary, and treatment is as effective as topical benzoyl peroxide 5%, isotretinoin 0.05%, and erythromycin 2%.[48] Azelaic acid is thought to be an effective acne treatment due to its antibacterial, anti-inflammatory, and antikeratinizing properties.[42] Azelaic acid may cause skin irritation but is otherwise very safe.[49]


In women, acne can be improved with the use of any combined oral contraceptive.[50] The combinations that contain third or fourth generation progestins such as desogestrel, norgestimate or drospirenone may theoretically be more beneficial.[50] Antiandrogens such as cyproterone acetate and spironolactone have also been used successfully to treat acne.[24] Hormonal therapies should not be used to treat during pregnancy or lactation as they have been associated with certain birth defects such as hypospadias and feminization of the male fetus.[24]

Topical retinoids[edit]

Topical retinoids are medications that possess anti-inflammatory properties and work by normalizing the follicle cell life cycle.[5] They are a first-line acne treatment for people with dark colored skin and are known to lead to faster improvement of post inflammatory hyperpigmentation.[21] This class includes tretinoin (category C), adapalene (category C), and tazarotene (category X).[24] Like isotretinoin, they are related to vitamin A,[5] but are administered topically and generally have much milder side effects. They can, however, cause significant irritation of the skin. The retinoids appear to influence the cell life cycle in the follicle lining. This helps prevent the hyperkeratinization of these cells that can create a blockage. Retinol, a form of vitamin A, has similar, but milder, effects and is used in many over-the-counter moisturizers and other topical products. Topical retinoids often cause an initial flare-up of acne and facial flushing.

Oral retinoids[edit]

Isotretinoin is very effective for severe acne as well as moderate acne refractory to other treatments.[12] Improvement is typically seen after one to two months of use. After a single course, about 80% of people report an improvement with more than 50% reporting complete remission.[12] About 20% of people require a second course.[12] A number of adverse effects may occur including: dry skin, nose bleeds, muscle pains, increased liver enzymes, and increased lipid levels in the blood.[12] If used during pregnancy, there is a high risk of abnormalities in the baby and thus women of child bearing age are required to use effective birth control.[12] There is no clear evidence that use of oral retinoids increases the risk of psychiatric side effects such as depression and suicidality.[12]


The aldosterone antagonist spironolactone is an effective treatment for acne in adult women, but is not approved by the United States' Food and Drug Administration for this purpose.[21] Spironolactone is thought to be a useful acne treatment due to its ability to block the androgen receptor at higher doses.[21] It may be used with or without an oral contraceptive.[21]

Combination therapy[edit]

Combination therapy using medications of different classes together, each with a different mechanism of action, has been demonstrated to be a more efficacious approach to acne treatment than monotherapy.[24] Frequently used combinations include the following: antibiotic + benzoyl peroxide, antibiotic + topical retinoid, or topical retinoid + benzoyl peroxide.[24]


Comedo extraction may temporarily help those with comedones that do not improve with standard treatment.[8] A procedure with high patient satisfaction[quantify] for immediate relief is the injection of corticosteroids into the inflamed acne comedone.[5] There is no evidence that microdermabrasion is effective.[8]

Light therapy is a method that involves delivering intense pulses of light to the area with acne sometimes following the application of a sensitizing substance (such as aminolevulinic acid).[51] This process is thought to kill bacteria and decrease the size and activity of the glands that produce sebum.[51] As of 2012, evidence for light therapy and lasers is insufficient to recommend routine use.[8] Light therapy is expensive and while it appears to provide short term benefit, there is a lack of long term outcome data or data in those with severe acne.[5][52]

Dermabrasion is an effective therapeutic procedure for reducing the appearance of superficial atrophic scars of the boxcar and rolling varieties.[19] Ice pick scars do not respond well to treatment with dermabrasion due to their depth.[19] However, the procedure is painful and has many potential side effects such as skin sensitivity to sunlight, redness, and decreased pigmentation of the skin.[19] The procedure has fallen out of favor with the introduction of laser resurfacing.[19]

Laser resurfacing can be used to reduce the scars left behind by acne.[53] In a 2012 review of acne scar treatments, ablative fractional photothermolysis laser resurfacing was found to be more effective than non-ablative fractional photothermolysis, but was associated with higher rates of postinflammatory hyperpigmentation (usually about 1 month duration), facial redness (usually for 3-14 days), and pain during the procedure.[54]

Chemical peels can also be used to reduce the appearance of acne scars.[19] Mild chemical peels include those using glycolic acid, lactic acid, salicylic acid, Jessner's solution, or a lower concentration (20%) of trichloroacetic acid. These peels only affect the epidermal layer of the skin and can be useful in the treatment of superficial acne scars as well as skin pigmentation changes from inflammatory acne.[19] Higher concentrations of trichloroacetic acid (30-40%) are considered to be medium strength peels and affect skin as deep as the papillary dermis.[19] Formulations of trichloroacetic acid concentrated to 50% or more are considered to be deep chemical peels.[19] Medium and deep strength chemical peels are more effective for deeper atrophic scars, but are more likely to cause side effects such as skin pigmentation changes, infection, or milia.[19]

For people with cystic acne, boils can be drained through surgical lancing.[55]

Alternative medicine[edit]

Numerous natural products have been investigated for treating people with acne.[56] A topical application of tea tree oil has been suggested.[57] Evidence is insufficient to support their use.[58]


Acne usually improves around the age of 20 but may persist into adulthood.[45] Permanent physical scarring may occur.[12] There is good evidence to support the idea that acne has a negative psychological impact and worsens mood, lowers self-esteem, and is associated with a higher risk of anxiety, depression, and suicidal thoughts.[35]


Globally acne affects approximately 650 million people, or about 9.4% of the population, as of 2010.[59] It affects almost 90% of people in Western societies during their teenage years and may persist into adulthood.[12] Post-adolescent acne (acne after age 25) has an incidence of 54% in women and 40% in men.[24] Acne vulgaris has a lifetime prevalence of 85%.[24] About 20% have moderate or severe cases.[29] Rates appear to be lower in rural societies[14] and it may not occur in the non-Westernized people of Papua New Guinea and Paraguay.[29] It is slightly more common in females than males (9.8% versus 9.0%).[59] In those over 40 years old, 1% of males and 5% of females still have problems.[12] It affects people of all ethnic groups,[60] and it is not clear if race affects rates of disease.[29]

Acne affects 40 to 50 million people in the United States (16%) and approximately 3 to 5 million in Australia (23%).[61] In the United States, acne tends to be more severe in Caucasians than people of African descent.[5]



A vaccine against inflammatory acne has been tested successfully in mice, but has not yet been proven to be effective in humans.[68]

In 2007, the first genome sequencing of a P. acnes bacteriophage (PA6) occurred which should greatly enhance the development of a potential bacteriophage therapy to treat acne and, therefore, overcome the significant problems associated with long-term antibiotic therapy and bacterial resistance.[69]


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External links[edit]

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