Acne vulgaris:

Acne vulgaris (or simply acne) is a long-term skin disease that occurs when hair follicles become clogged with dead skin cellsand oil from the skin.[1] Acne is characterized by areas of blackheads, whiteheads, pimples, and greasy skin, and may result inscarring.[2][3][4] The resulting appearance can lead to anxiety, reduced self-esteem and, in extreme cases, depression or thoughts of suicide. 

Genetics is thought to be the cause in 80% of cases.[3] The role of diet and cigarette smoking is unclear and neither cleanlinessnor sunlight appear to be involved.[3][7][8] Acne primarily affects skin with a greater number of oil glands, including the face, upper part of the chest, and back.[9] During puberty, in both sexes, acne is often brought on by an increase in androgens such astestosterone.[10] Excessive growth of the bacteria Propionibacterium acnes, which is normally present on the skin, is often involved.[10]

Many treatment options are available to improve the appearance of acne, including lifestyle changes, procedures, and medications. Eating fewer simple carbohydrates like sugar may help.[11] Topical azelaic acid, benzoyl peroxide, and salicylic acidare commonly used treatments.[12] Antibiotics and retinoids are available in both topical and oral formulations to treat acne.[12]However, resistance to antibiotics may develop.[13] A number of birth control pills may be useful for preventing acne in women.[12]Oral isotretinoin is usually reserved for severe acne due to greater potential side effects.[12] Early and aggressive treatment is advocated by some to lessen the overall long-term impact to individuals.

In 2013, acne was estimated to affect 660 million people globally, making it the 8th most common disease worldwide.[14][15] Acne occurs most commonly during adolescence, affecting an estimated 80–90% of teenagers in the Western world.[16][17][18] Lower rates are reported in some rural societies.[18][19] People may also be affected before and after puberty.[20] Though it becomes less common in adulthood than in adolescence, nearly half of people in their twenties and thirties continue to have acne. About 4% continue to have difficulties into their forties.[3]

Classification

Acne is commonly classified by severity as mild, moderate, or severe. This type of categorization can be an important factor in determining the appropriate treatment regimen.Mild acne is classically defined as open (blackheads) and closed (whiteheads) comedones limited to the face with occasional inflammatory lesions Acne may be considered to be of moderate severity when a higher number of inflammatory papules and pustules occur on the face compared to mild cases of acne, and acne lesions also occur on the trunk of the body.[17] Lastly, 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 have been referred to as cysts in the past, and the term nodulocystic has been used in the medical literature to describe severe cases of inflammatory acne.However, since true cysts are rare in those with acne, the term severe nodular acne is now the preferred terminology. Collected by Wikipedia