The acid mantle is a thin oily film that sits on top of the outmost layer of our skin. For most people, the pH of the acid mantle is about 4.5 to 5.5. Why is our skin naturally acidic at the surface? Our slightly acidic skin helps to fight off harmful bacteria. Many of the contaminants that might enter our skin, such as chemicals from the atmosphere and harmful bacteria, are alkaline in nature (i.e., they have a pH of higher than 7). Our skin’s natural acidity neutralizes these chemicals and bacteria, much the same way the milk of magnesia neutralizes stomach acid when we have heartburn. Neutralizing these harmful contaminants is part of the body’s defense system. Maintaining the skin pH at the proper level is vital to protecting ourselves from harmful bacteria which can lead to acne, infection, or irritation.
Most of us use soap and water to clean our faces without realizing that this may not be beneficial to us. Soapy water is highly alkaline (with a pH of 12, see chart) while our skin is naturally acidic (with a pH of approximately 5). Soapy water is commonly used to clean our faces because it removes the natural oils from the skin. While this leaves our skin with that “clean feeling," soap is actually neutralizing our skins acid pH thereby stripping away our natural defense systems. Particularly for those of us that wash our faces 2, 3, or 4 times a day because of a problem condition like acne, stripping away the acid mantle can actually worsen our condition. Similarly it is important for us to know the pH of any cleansers, moisturizers, makeup and other products we use so that we don’t remove the protective oils and acid mantle from our skin.
The acid mantle, the combination of sebum (oil) and perspiration, on the skin's surface protects the skin and renders the skin less vulnerable to damage. It also protects from attack by environmental factors such as the sun and wind and leaves it less prone to dehydration. Normal skin pH is somewhat acidic and in the range of 4.2. to 5.6. It varies from one part of the body to another and, in general, the pH of a man's skin is lower (more acidic) than a woman's. The acid mantle inhibits the growth of foreign bacteria and fungi causing the skin to remain healthier and have fewer blemishes. Acne, allergies and other skin problems become more severe when the skin become more alkaline.
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Sebum, Sweat, Skin pH and Acid Mantle
Sebum is an oily secretion produced by sebacious glands, tiny ducts adjacent to hair follicles. Sebum is secreted into the follicle, from which it spreads over the hair and skin. The main role of sebum is to waterproof the skin and hair. Both excess and lack of sebum are undesirable. Excess sebum is associated with oily skin and acne. It is particularly common in adolescents as the increased levels of sex hormones stimulate sebum production. Lack of sebum, which is common in middle and older age, leads to skin dryness and accelerates wrinkle formation.
Sweat is a salty, watery solution produced by sweat glands, numerous microscopic channels opening onto the skin surface. As sebum and sweat mix up on the skin surface, they form a protective layer often referred to as the acid mantle . Acid mantle has a particular level of acidity characterized by pH from about 4 to 5.5. A pH of 7 is considered neutral, above 7 is alkaline, and below is acidic. The pH of acid in the human stomach, for example, is usually from 1 to 2, which is highly acidic. The skin, on the other hand, is mildly acidic. In addition to helping protect skin from "the elements" (such as wind or pollutants), acid mantle also inhibits the growth of harmful bacteria and fungi. If acid mantle is disrupted or loses its acidity, the skin becomes more prone to damage and infection. The loss of acid mantle is one of the side-effects of washing the skin with soaps or detergents of moderate or high strength.
Source: http://www.smartskin...logy/sebum.html
Here in lies the problem even with so-called pH leveled soaps/topicals. Everyone's acid mantle pH is different. No product can account for correctly bring your acid mantle back to a "normal" pH.
Edited by steven m jacobson, 26 December 2011 - 07:01 PM.



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