Normally, essential natural skin oil excreted by the sebaceous glands does its lubricating and moisturizing work and drains off. Oily skin not only attracts dusts but also continuously shed the dead cells. It can also involve infected or otherwise abnormal hair follicles.
Another cause of acne is the high levels of insulin produced by processed carbohydrates in body that can creat blockages in the pores and extra oil under the skin. Both teenagers and adults can have acne. It may also be caused by hormonal changes.
These bacteria usually live harmlessly on your skin but when the conditions are right, they grow. They feed off the sebum and produce substances that cause an immune response. This inflames the skin and creates the redness associated with spots.
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