• Acne is a common skin condition which leads to spots on the face, back and chest- it is most common in the teens and twenties, though some people also get it later in life.
• Normal skin has "sebaceous glands" which produce natural oils.
• During puberty, the skin produces more of these oils, which may cause blockage of the sebaceous glands.
• The trapped oils in the glands allow bacteria (Propionibacterium acnes) to multiply. Dead skin cells may also build up in the pores.
• This in turn results in an immune reaction, inflammation and infection in the skin.
• Experts are not sure why some people get acne while others don't, but there seem to be some factors involved, including: hormonal changes during puberty, PCOS (polycystic ovarian syndrome), other hormonal disorders, smoking, stress, exhaustion, using oily skin products, family history of acne. 
• Some medications may make acne worse, such as progesterone only contraceptives, steroid creams (used in eczema), anabolic steroids, Lithium and some antiepileptic medications.
• It is not certain whether diet has any effect on acne, though some people find that cutting down on processed meats and refined carbohydrates may help. Others report that eliminating milk-based products helps, though there is no clear scientific evidence this is effective for most people. There is also no evidence about any benefits from vegan or vegetarian diets, or from taking probiotics.

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