Acne vulgaris (or simply acne) is a long-term skin disease that occurs when hair follicles become clogged with dead skin cells and oil from the skin. Acne is characterized by areas of blackheads, whiteheads, pimples, and greasy skin, and may result in scarring. The resulting appearance can lead to anxiety, reduced self-esteem and, in extreme cases, depression or thoughts of suicide.
 
 
Acne is commonly classified by severity as mild, moderate, or severe. 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.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.
 
Signs and symptoms
 
Typical features of acne include seborrhea (increased oil secretion), microcomedones, comedones, papules, pustules, nodules (large papules), and in many cases scarring. The appearance of acne varies with skin color. It may result in psychological and social problems.
 
Scars
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. The scar is created by an abnormal form of healing following this dermal inflammation. Scarring is most likely to occur with severe nodular acne, but may occur with any form of acne vulgaris.[24] 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.
 
Pigmentation
Postinflammatory hyperpigmentation (PIH) is usually the result of nodular acne lesions. 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.Pigmented scar is a common but misleading term, as it suggests the color change is permanent. Often, PIH can be prevented by avoiding aggravation of the nodule. 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.
 
 Cause
Hormonal
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 follicular glands to grow larger and make more sebum. Acne that first develops between the ages of 21 and 25 is uncommon. Several hormones have been linked to acne, including the androgens testosterone, dihydrotestosterone (DHT), and dehydroepiandrosterone sulfate (DHEA-S), as well as insulin-like growth factor 1 (IGF-1) and growth hormone (GH). 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 extremely 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. An increase in androgen (and sebum) synthesis may also be seen during pregnancy. Acne can be a side effect of testosterone replacement therapy or of anabolic steroid use.Anabolic steroids are commonly found in over-the-counter bodybuilding supplements.
 
Infectious
Propionibacterium acnes (P. acnes) is the anaerobic bacterium species that is widely suspected to contribute to the development of acne, but its exact role in this process is not entirely clear.There are specific sub-strains of P. 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 either changing, perpetuating, or adapting to the abnormal cycle of inflammation, oil production, and inadequate sloughing of dead skin cells from acne pores. One particularly virulent strain has been circulating in Europe for at least 87 years. Infection with the parasitic mite Demodex is associated with the development of acne. However, it is unclear whether eradication of these mites improves acne.
 
Diet
The relationship between diet and acne is unclear, as there is no high-quality evidence which establishes any definitive link. High-glycemic-load diets have been found to have different degrees of effect on acne severity by different studies. There may be a relationship between acne and insulin metabolism, and one trial found a relationship between acne and obesity. Vitamin B12 may trigger skin outbreaks similar to acne (acneiform eruptions), or exacerbate existing acne, when taken in doses exceeding the recommended daily intake.
 
Psychological
 
 
Overall, few high-quality studies have been performed which demonstrate that stress causes or worsens acne. While the connection between acne and stress has been debated, some research indicates that increased acne severity is associated with high stress levels in certain settings (e.g., in association with the hormonal changes seen in premenstrual syndrome).
 
Acne Rosacea is a long term skin condition characterized by facial redness, small and superficial dilated blood vessels on facial skin, papules, pustules, and swelling. Rosacea typically begins as redness on the central face across the cheeks, nose, or forehead, but can also less commonly affect the neck, chest, ears, and scalp.In some cases, additional signs, such as semipermanent redness, dilation of superficial blood vessels on the face, red domed papules (small bumps) and pustules, red gritty eyes, burning and stinging sensations, and in some advanced cases, a red lobulated nose (rhinophyma), may develop.