Lanolin (from Latin lāna 'wool' and oleum 'oil'), also called wool fat, wool yolk, wool wax, sheep grease, sheep yolk, or wool grease, is a wax secreted by the sebaceous glands of wool-bearing animals. Lanolin used by humans comes from domestic sheep breeds that are raised specifically for their wool. Historically, many pharmacopoeias have referred to lanolin as wool fat (adeps lanae); however, as lanolin lacks glycerides (glycerol esters), it is not a true fat. Lanolin primarily consists of sterol esters instead. Lanolin's waterproofing property aids sheep in shedding water from their coats. Certain breeds of sheep produce large amounts of lanolin. Lanolin in nature protects wool and skin from climate and the environment; it is also involved in skin (integumental) hygiene. Lanolin and its derivatives are used in the protection, treatment, and beautification of human skin.
Composition A typical high-purity grade of lanolin is composed predominantly of long chain waxy esters (approximately 97% by weight) with the remainder being lanolin alcohols, lanolin acids and lanolin hydrocarbons. An estimated 8,000 to 20,000 different types of lanolin esters are present in lanolin, resulting from combinations between the different lanolin acids and alcohols; about 200 acids and 100 alcohols had been identified by 1986. In addition to being useful itself, lanolin's complex composition of long-chain esters, hydroxyesters, diesters, lanolin alcohols, and lanolin acids makes it a starting point for the production of a whole spectrum of lanolin derivatives with wide-ranging chemical and physical properties. The main derivatisation routes include hydrolysis, fractional solvent crystallisation, esterification, hydrogenation, alkoxylation and quaternisation. Lanolin derivatives obtained from these processes are used widely in both cosmetics and skin treatment products. Hydrolysis of lanolin yields lanolin alcohols and lanolin acids. Lanolin alcohols are a rich source of cholesterol, an important skin lipid, and are powerful water-in-oil emulsifiers; they have been used extensively in skincare products for over 100 years. Approximately 40% of the acids derived from lanolin are alpha-hydroxy acids (AHAs). The use of AHAs in skin care products has attracted much attention. Details of the AHAs isolated from lanolin can be seen in the table below.
Production Crude lanolin constitutes about 5–25% of the weight of freshly shorn wool. Wool from one Merino sheep produces about 250–300 ml (9–11 imp fl oz; 8–10 US fl oz) of recoverable wool grease. Lanolin is extracted by washing the wool in hot water with a special wool-scouring detergent to remove dirt, wool grease (crude lanolin), suint (sweat salts), and anything else stuck to the wool. The wool grease is continuously removed during this washing process by centrifuge separators, which concentrate it into a waxlike substance which melts at approximately 38 °C (100 °F).
Applications
Lanolin and its many derivatives are used extensively both for personal care (e.g. cosmetics, facial cosmetics, lip products) and healthcare (topical liniments). Lanolin is also used in lubricants, rust-preventive coatings, shoe polish, and other commercial products. Lanolin is a relatively common allergen, causing what is often misunderstood as a wool allergy. However, allergy to a lanolin-containing product is difficult to pinpoint, and often different forms of lanolin may not cause an allergic reaction in the same person. Patch testing can be done if a lanolin allergy is suspected. It is frequently used in protective baby skin treatment. It is also used for sore nipples from breastfeeding, but health authorities recommend alternative methods first, including nipple cleaning, improving baby positioning, and ultimately expressing milk by hand. Lanolin is reported to have soothing properties, but there is a lack of research. Lanolin is used commercially in many industrial products ranging from rust-proof coatings to lubricants. Some sailors use lanolin to create slippery surfaces on their propellers and stern gear to which barnacles cannot adhere. Commercial products (e.g. Lanocote) containing up to 85% lanolin are used to prevent corrosion in marine fasteners, especially when two different metals are in contact with each other in the presence of saltwater. The water-repellent properties make it valuable in many applications as a lubricant grease where corrosion would otherwise be a problem. 7-Dehydrocholesterol from lanolin is used as a raw material for producing vitamin D3 by irradiation with ultraviolet light. Baseball players often use it to soften and break in their baseball gloves—shaving cream with lanolin is popularly used for this. Anhydrous liquid lanolin, combined with parabens, has been used in trials as artificial tears to treat dry eye. Anhydrous lanolin is also used as a lubricant for brass musical instrument tuning slides. Lanolin can also be applied to woollen garments to make them water- and dirt-repellent, such as for cloth diaper covers. Lanolin is used in lip balm products such as Carmex. It can irritate the lips of some people. Lanolin is sometimes used by people on continuous positive airway pressure therapy to reduce irritation with masks, particularly nasal pillow masks that often create sore spots in the nostrils. Lanolin is a popular additive to moustache wax, particularly 'extra-firm' varieties. Lanolin is used as a primary lubricating component in aerosol-based brass lubricants when reloading ammunition. It is mixed warm 1:12 with ethanol, usually about 99% pure, which acts as a carrier which evaporates quickly after application, leaving a thin film of lanolin which protects against brass seizing in resizing dies. Lanolin is used as a lubricant for leather and fur, and in polishes and protective coatings for shoes and leather goods. Lanolin, when mixed with ingredients such as neatsfoot oil, beeswax and glycerol, is used in various leather treatments, for example in some saddle soaps and in leather care products.
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