Each biological system possesses a widely unrecognized buffer system to maintain acid-base balance to a specific pH. Our lives are dependent on the functioning of buffer systems. A buffer system is a solution that resists a change in pH when acids or bases are added. The skin possesses a fairly high buffer capacity, which is determined by the amount of H+ or OH- ions that is needed until the pH value of a solution changes by the unit 1. Buffers contain a weak or medium strong acid (base) and the corresponding salt. Buffers that show a pKa in the range of the Stratum corneum surface pH are most important for the skin. Buffer capacity is reduced both in baby skin and in aged skin. External factors, water, and detergent may reduce the local buffer capacity because of the elution of buffer chemicals leading to increased pH and irritative contact dermatitis. Inflammatory diseases, including atopic dermatitis, psoriasis, and acne vulgaris, which show an increased pH should probably also have reduced buffer capacities. For the treatment of the skin diseases and in aged skin, emollient with a pH that is slightly more acidic than the average normal pH and an appropriate buffer capacity should be preferably used.
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