![\"whitewillow02\"](\"https:\/\/ulprospector.ul.com\/media\/2016\/04\/whitewillow02-1.jpg\")
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Salicylic acid <\/a>(Hydroxybenzoic acid) is a white, colorless crystalline powder that occurs naturally in white willow.<\/a> The active extract of the bark, salicin, is a glucoside<\/a> of salicylic acid.<\/p>\n The first recorded use of salicylates dates back 4,000 years to the Sumerians who used willow extracts for pain relief. Ancient civilizations in Mesopotamia used willow extracts to treat fever, pain, and inflammation. Both Chinese and Greek civilizations employed willow bark for medical use more than 2,000 years ago, and the Chinese also used poplar bark and willow shoots to treat rheumatic fever, colds, hemorrhages, and goiter. Native Americans were known to have widely used SA in the form of willow bark, to treat pain, fever, and inflammation.<\/p>\n In 1828 Johann Buchner was the first to distill from willow bark the substance he called \u201cSalicin\u201d after the Latin name for the willow tree, Salix alba. In 1829, French chemist Henri LaRoux perfected the extraction technique. In 1853, Charles Gerhardt, another Frenchman, invented Aspirin, though it wasn\u2019t marketed until the Bayer company patented the formula in 1899.<\/p>\n SA is commercially prepared by treating sodium phenolate (the sodium salt of phenol) with carbon dioxide at high pressure (100 atm.) and high temperature (390K), a method known as the Kolbe-Schmitt reaction. Acidification of the product with sulfuric acid gives SA.<\/p>\n Prospector has over 100 listings for salicylic acid products. View technical data, order samples and more now!<\/p>\n Molecular weight 138.12 Typical OTC personal care applications are for the treatment of acne where it is monographed from .5-2% and dandruff 1.8-3%. Triethanolamine salicylate is also used as a topical analgesic, but this indication has not been approved by the FDA. It is also monographed for the removal of warts at 15%. Cosmetic applications include chemical peels and antiaging products to increase cell turnover and reduce wrinkles. The key mode of action for SA is increased keratolytic activity in these applications.<\/p>\n When formulating clear, water-based solutions, the key consideration is solubilization. SA can be solubilized using ethanol<\/a>, glycols<\/a>, and nonionic ethoxylated fatty alcohols.<\/p>\n The PH of the formulation is also a critical factor since it dramatically affects both solubility and efficacy. When formulating 2% SA at a PH of 3, the best strategy is to solubilize the SA using 42% ethanol and isoceteth 20 (Brij IC20 <\/a>\u2013\u00a0Croda). Since SA easily penetrates skin, adding a material like Polyolprepolymer-15 (PEG-8 \/ SMDI Copolymer <\/a>\u2013 Barnet Products) can be useful to increase the deposition of salicylic acid in the upper layers of the stratum corneum and to reduce skin irritation.<\/p>\n Another consideration\u00a0when formulating at a PH of 3 is to avoid using ester-based materials that can hydrolyze. SA formulations should contain a good chelant to prevent discoloration due to reacting with trace iron. SA can also be formulated into alcohol-free, oil-in-water emulsions by first solubilizing the SA using an emollient like Arlamol PS15E<\/a> (PPG-15 Stearyl Ether \u2013 Croda). This oil phase can then be emulsified into an aqueous gel containing acid-stable thickeners like Sepigel 305,<\/a> Aristoflex AVC<\/a>, or Synthalen CR<\/a>. (Polyquaternium 37 \u2013 3V).<\/p>\n References<\/strong><\/p>\n
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\nKey chemical properties<\/h3>\n
\nSublimes at 70C
\n.18% soluble in water @20C, .41% @40C, 1.7% @75C
\n13.8% soluble in Ethanol @ 20C
\nSolubility in Glycerin 1.63%, 20% Ethanol will solubilize ~.5% SA<\/p>\n\n
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