Acidum Salicylicum or Salicylic Acid For medical use. exp. date: 30.10.2014 lot No. 081031 Salicylic Acid is a beta hydroxy acid derived from the bark of the willow tree. Beta hydroxy acids (BHA) is a larger molecule than their cousin, alpha hydroxy acids. The larger molecule size keeps the beta hydroxy acid on the surface of the skin allowing it to more effectively penetrate and exfoliate within the pore. This action within the pores make it an ideal exfoliant for use o?n acne and acne-prone skin. The larger molecule size of salicylic acid produces less irritation than alpha hydroxy acids, making it a welcome alternative for those with sensitive skin. Salicylic Acid is best on acne-prone and sensitive skin types. The pore-cleansing properties of salicylic acid make it a more effective comedone fighter. Those with sensitive skin who cannot tolerate alpha hydroxy acids may find that they are able to use salicylic acid with good results. Derivation Salicylic Acid is obtained by combining carbolic acid with caustic soda, and subjecting this compound to dry carbonic acid under the influence of heat, the portion of salicylate of sodium remaining behind after the carbolic acid distills over being saturated, in the form of a hot, aqueous solution, with muriatic acid, which liberates the salicylic acid in small crystals. The crystals are washed, dissolved in hot water, and by re-crystallization, obtained in the form of a powder of a light brown color, which is then bleached until it is quite white. The coloring matter, however, which is present, does not interfere with its efficacy. It is sometimes obtained from the product of plants, such as wintergreen. It has no smell, a slight taste, and is soluble in alcohol and ether and in hot water and glycerine. It can also be obtained from salicin, the vegetable principle existing in willow, poplar, etc., and from oil of gaultheria (wintergreen) and from spiraea ulmariae (meadow sweet).