acne acne acne, also known as acne vulgaris, is a long-term skin condition that occurs when dead skin cells and oil from the skin clog hair follicles. typical features of the condition include blackheads or whiteheads, pimples, oily skin, and possible scarring. it primarily affects skin with a relatively high number of oil glands, including the face, upper part of the chest, and back. the resulting appearance can lead to lack of confidence, anxiety, reduced self-esteem, and, in extreme cases, depression or thoughts of suicide. acneother namesacne vulgarisacne vulgaris in an 18-year-old male during pubertyspecialtydermatologysymptomsblackheads, whiteheads, pimples, oily skin, scarringcomplicationsanxiety, reduced self-esteem, depression, thoughts of suicideusual onsetpubertyrisk factorsgeneticsdifferential diagnosisfolliculitis, rosacea, hidradenitis suppurativa, miliariatreatmentlifestyle changes, medications, medical proceduresmedicationazelaic acid, benzoyl peroxide, salicylic acid, antibiotics, birth control pills, co-cyprindiol, retinoids, isotretinoinfrequency633 million affected (2015) susceptibility to acne is primarily genetic in 80% of cases. the roles of diet and cigarette smoking in the condition are unclear, and neither cleanliness nor exposure to sunlight appear to play a part. in both sexes, hormones called androgens appear to be part of the underlying mechanism, by causing increased production of sebum. another common factor is the excessive growth of the bacterium cutibacterium acnes, which is present on the skin. treatments for acne are available, including lifestyle changes, medications, and medical procedures. eating fewer simple carbohydrates such as sugar may minimize the condition. treatments applied directly to the affected skin, such as azelaic acid, benzoyl peroxide, and salicylic acid, are commonly used. antibiotics and retinoids are available in formulations that are applied to the skin and taken by mouth for the treatment of acne. however, resistance to antibiotics may develop as a result of antibiotic therapy. several types of birth control pills help prevent acne in women. medical professionals typically reserve isotretinoin pills for severe acne, due to greater potential side effects. early and aggressive treatment of acne is advocated by some in the medical community to decrease the overall long-term impact on individuals. in 2015, acne affected approximately 633 million people globally, making it the eighth-most common disease worldwide. acne commonly occurs in adolescence and affects an estimated 80–90% of teenagers in the western world. some rural societies report lower rates of acne than industrialized ones. children and adults may also be affected before and after puberty. although acne becomes less common in adulthood, it persists in nearly half of affected people into their twenties and thirties, and a smaller group continues to have difficulties in their forties. classification the severity of acne vulgaris (gr. ἀκµή, "point" + l. vulgaris, "common") can be classified as mild, moderate, or severe to determine an appropriate treatment regimen. there is no universally accepted scale for grading acne severity. the presence of clogged skin follicles (known as comedones) limited to the face with occasional inflammatory lesions defines mild acne. moderate severity acne is said to occur when a higher number of inflammatory papules and pustules occur on the face, compared to mild cases of acne, and appear on the trunk of the body. severe acne is said to occur when nodules (the painful 'bumps' lying under the skin) are the characteristic facial lesions, and involvement of the trunk is extensive. large nodules were previously called cysts. the term nodulocystic has been used in the medical literature to describe severe cases of inflammatory acne. true cysts are rare in those with acne, and the term severe nodular acne is now the preferred terminology. acne inversa (l. invertō, "upside-down") and acne rosacea (rosa, "rose-colored" + -āceus, "forming") are not forms of acne and are alternate names that respectively refer to the skin conditions hidradenitis suppurativa (hs) and rosacea. although hs shares certain overlapping features with acne vulgaris, such as a tendency to clog skin follicles with skin cell debris, the condition otherwise lacks the hallmark features of acne and is therefore considered a distinct skin disorder. signs and symptoms a severe case of nodular acnenodular acne on the backa typical case of a teenager with acne, pimples in various parts of the head. typical features of acne include increased secretion of oily sebum by the skin, microcomedones, comedones, papules, nodules (large papules), pustules, and often results in scarring. the appearance of acne varies with skin color. it may result in psychological and social problems. scars acne scars are caused by inflammation within the dermis and are estimated to affect 95% of people with acne vulgaris. abnormal healing and dermal inflammation create the scar. scarring is most likely to take place with severe acne but may occur with any form of acne vulgaris. acne scars are classified based on whether the abnormal healing response following dermal inflammation leads to excess collagen deposition or loss at the site of the acne lesion. atrophic acne scars have lost collagen from the healing response and are the most common type of acne scar (accounting for approximately 75% of all acne scars). ice-pick scars, boxcar scars, and rolling scars are subtypes of atrophic acne scars. boxcar scars are round or ovoid indented scars with sharp borders and vary in size from 1.5–4 mm across. ice-pick scars are narrow (less than 2 mm across), deep scars that extend into the dermis. rolling scars are broader than ice-pick and boxcar scars (4–5 mm across) and have a wave-like pattern of depth in the skin. hypertrophic scars are uncommon and are characterized by increased collagen content after the abnormal healing response. they are described as firm and raised from the skin. hypertrophic scars remain within the original margins of the wound, whereas keloid scars can form scar tissue outside of these borders. keloid scars from acne occur more often in men and people with darker skin, and usually occur on the trunk of the body. in november 2021 a study was published exposing the consensus of twenty-four renowned international plastic surgeons and dermatologists about the most effective energy-based devices for the treatment of acne scars. pigmentation after an inflamed nodular acne lesion resolves, it is common for the skin to darken in that area, which is known as postinflammatory hyperpigmentation (pih). the inflammation stimulates specialized pigment-producing skin cells (known as melanocytes) to produce more melanin pigment, which leads to the skin's darkened appearance. pih occurs more frequently in people with darker skin color. pigmented scar is a common term used for pih, but is misleading as it suggests the color change is permanent. often, pih can be prevented by avoiding any aggravation of the nodule and can fade with time. however, untreated pih can last for months, years, or even be permanent if deeper layers of skin are affected. even minimal skin exposure to the sun's ultraviolet rays can sustain hyperpigmentation. daily use of spf 15 or higher sunscreen can minimize such a risk. whitening agents like azelaic acid, arbutin or else may be used to improve hyperpigmentation. causes risk factors for the development of acne, other than genetics, have not been conclusively identified. possible secondary contributors include hormones, infections, diet, and stress. studies investigating the impact of smoking on the incidence and severity of acne have been inconclusive. sunlight and cleanliness are not associated with acne. genes acne appears to be highly heritable; genetics explain 81% of the variation in the population. studies performed in affected twins and first-degree relatives further demonstrate the strongly inherited nature of acne. acne susceptibility is likely due to the influence of multiple genes, as the disease does not follow a classic (mendelian) inheritance pattern. these gene candidates include certain variations in tumor necrosis factor-alpha (tnf-alpha), il-1 alpha, and cyp1a1 genes, among others. the 308 g/a single nucleotide polymorphism variation in the gene for tnf is associated with an increased risk for acne. acne can be a feature of rare genetic disorders such as apert's syndrome. severe acne may be associated with xyy syndrome. hormones hormonal activity, such as occurs during menstrual cycles and puberty, may contribute to the formation of acne. during puberty, an increase in sex hormones called androgens causes the skin follicle glands to grow larger and make more oily sebum. the androgen hormones testosterone, dihydrotestosterone (dht), and dehydroepiandrosterone (dhea) are all linked to acne. high levels of growth hormone (gh) and insulin-like growth factor 1 (igf-1) are also associated with worsened acne. both androgens and igf-1 seem to be essential for acne to occur, as acne does not develop in individuals with complete androgen insensitivity syndrome (cais) or laron syndrome (insensitivity to gh, resulting in very low igf-1 levels). medical conditions that commonly cause a high-androgen state, such as polycystic ovary syndrome, congenital adrenal hyperplasia, and androgen-secreting tumors, can cause acne in affected individuals. conversely, people who lack androgenic hormones or are insensitive to the effects of androgens rarely have acne. pregnancy can increase androgen levels, and consequently, oily sebum synthesis. acne can be a side effect of testosterone replacement therapy or anabolic steroid use. over-the-counter bodybuilding and dietary supplements often contain illegally added anabolic steroids. infections the anaerobic bacterial species cutibacterium acnes (formerly propionibacterium acnes) contributes to the development of acne, but its exact role is not well understood. there are specific sub-strains of c. acnes associated with normal skin and others with moderate or severe inflammatory acne. it is unclear whether these undesirable strains evolve on-site or are acquired, or possibly both depending on the person. these strains have the capability of changing, perpetuating, or adapting to the abnormal cycle of inflammation, oil production, and inadequate sloughing of dead skin cells from acne pores. infection with the parasitic mite demodex is associated with the development of acne. it is unclear whether eradication of the mite improves acne. diet high-glycemic-load diets have been found to have different degrees of effect on acne severity. multiple randomized controlled trials and nonrandomized studies have found a lower-glycemic-load diet to be effective in reducing acne. there is weak observational evidence suggesting that dairy milk consumption is positively associated with a higher frequency and severity of acne. milk contains whey protein and hormones such as bovine igf-1 and precursors of dihydrotestosterone. studies suggest these components promote the effects of insulin and igf-1 and thereby increase the production of androgen hormones, sebum, and promote the formation of comedones. available evidence does not support a link between eating chocolate or salt and acne severity. few studies have examined the relationship between obesity and acne. vitamin b12 may trigger skin outbreaks similar to acne (acneiform eruptions), or worsen existing acne when taken in doses exceeding the recommended daily intake. stress there are few high-quality studies to demonstrate that stress causes or worsens acne. despite being controversial, some research indicates that increased acne severity is associated with high stress levels in certain contexts, such as hormonal changes seen in premenstrual syndrome. other some individuals experience severe intensification of their acne when they are exposed to hot humid climates; this is due to bacteria and fungus thriving in warm, moist environments. this climate induced acne exacerbation has been termed tropical acne. mechanical obstruction of skin follicles with helmets or chinstraps can worsen pre-existing acne. however, when acne is caused by mechanical obstruction it is not considered a form of acne vulgaris when being very technical. it would be an other acneiform eruption known as acne mechanica. several medications can also worsen pre-existing acne; this condition is the acne medicamentosa form of acne. examples of such medications include lithium, hydantoin, isoniazid, glucocorticoids, iodides, bromides, and testosterone. when acne medicamentosa is specifically caused by anabolic–androgenic steroids it can simply be referred to as steroid acne. genetically susceptible individuals can get acne breakouts as a result of polymorphous light eruption; a condition triggered by sunlight and artificial uv light exposure. this form of acne is called acne aestivalis and it's specifically caused by intense uva light exposure. affected individuals usually experience seasonal acne breakouts on their upper arms, shoulder girdle, back, and chest. the breakouts typically occur one-to-three days after they've been exposed to intese uva radiation. unlike other forms of acne the condition spares the face; this could possibly be a result of the pathogenesis of polymorphous light eruption, in which areas of the skin that are newly exposed to intense ultraviolet radiation are affected. since faces are typically left uncovered at all stages of life there's little-to-no likelihood for an eruption to appear there. studies show that