Lanolin

This article is about the sheep grease. For the character, see U.S. Acres § Lanolin Sheep.
Wool fat tin (adeps lanae), at the Centre touristique de la Laine et de la Mode in Verviers, Belgium

Lanolin (from Latin lāna, ‘wool’, and oleum, ‘oil’), also called wool wax 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.[1][2] Lanolin primarily consists of sterol esters instead.[3] Lanolin's waterproofing property aids sheep in shedding water from their coats. Certain breeds of sheep produce large amounts of lanolin. There is an inverse correlation between fiber diameter and wool wax content.

Lanolin’s role in nature is to protect wool and skin against the ravages of climate and the environment; it also seems to play a role in skin (integumental) hygiene.[1] Lanolin and its many derivatives are used extensively in products designed for the protection, treatment and beautification of human skin.[1]

Composition

A typical high purity grade of lanolin is composed predominantly of long chain waxy esters (approximately 97% by weight) the remainder being lanolin alcohols, lanolin acids and lanolin hydrocarbons.[1]

An estimated 8,000 to 20,000 different types of lanolin esters are present in lanolin, resulting from combinations between the 200 or so different lanolin acids and the 100 or so different lanolin alcohols identified so far.[1][2]

Lanolin’s complex composition of long chain esters, hydroxy esters, diesters, lanolin alcohols, and lanolin acids means in addition to it being a valuable product in its own right, it is also the starting point for the production of a whole spectrum of lanolin derivatives, which possess wide-ranging chemical and physical properties. The main derivatisation routes include hydrolysis, fractional solvent crystallisation, esterification, hydrogenation, and alkoxylation[4] and quaternisation.[1][2][5] Lanolin derivatives obtained from these processes are used widely in both high-value 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 skin care products for over 100 years.[1] Notably, approximately 40% of the acids derived from lanolin are alpha hydroxy acids (AHAs).[1][2] The use of AHAs in skin care products has attracted a great deal of attention in recent years. Details of the AHA’s isolated from lanolin can be seen in the table below.

Type of lanolic acid Carbon chain length Number identified
Alpha hydroxy normal C
13–C
24 		12
Alpha hydroxy iso C
13–C
23 		6
Alpha hydroxy anteiso C
12–C
24 		7

Modern developments

In addition to general purity requirements, lanolin must meet official requirements for the permissible levels of pesticide residues. The Fifth Supplement of the United States Pharmacopoeia XXII published in 1992 was the first to specify limits for 34 named pesticides. A total limit of 40 ppm (or mg/kg) total pesticides was stipulated for lanolin of general use, with no individual limit greater than 10 ppm.[1]

A second monograph also introduced into the US Pharmacopoeia XXII in 1992 was entitled ‘Modified Lanolin.’ Lanolin conforming to this monograph is intended for use in more exacting applications, for example on open wounds. In this monograph, the limit of total pesticides was reduced to 3 ppm total pesticides, with no individual limit greater than 1 ppm.

In 2000, the European Pharmacopoeia introduced pesticide residue limits into its lanolin monograph. This requirement, which is generally regarded as the new quality standard, extends the list of pesticides to 40 and imposes even lower concentration limits.

Some very high purity grades of lanolin surpass monograph requirements. New products obtained using complex purification techniques produce lanolin esters in their natural state, removing oxidative and environmental impurities resulting in white, odourless, hypoallergenic lanolin. These ultra-high purity grades of lanolin are ideally suited to the treatment of dermatological disorders such as eczema and on open wounds.[6]

Lanolin attracted attention owing to a misunderstanding concerning its sensitising potential.[7] A study carried out at New York University Hospital in the early 1950s had shown about 1% of patients with dermatological disorders were allergic to the lanolin being used at that time. However, this figure was misinterpreted and taken out of context and became quoted as 1% of the general healthy (American) population. By one estimate, this simple misunderstanding of failing to differentiate between the general healthy population and patients with dermatological disorders exaggerates the sensitising potential of lanolin by 5,000–6,000 times.[7][8]

The European Cosmetics Directive, introduced in July 1976, contained a stipulation that cosmetics which contained lanolin should be labelled to that effect. This ruling was challenged immediately, and in the early 1980s, it was overturned and removed from the directive. Despite only being in force for a short period of time, this ruling did harm both to the lanolin industry and to the reputation of lanolin in general.[7] The Cosmetics Directive ruling only applied to the presence of lanolin in cosmetic products; it did not apply to the many hundreds of its different uses in dermatological products designed for the treatment of compromised skin conditions.

Modern analytical methods have revealed lanolin possesses a number of important chemical and physical similarities to human stratum corneum lipids; the lipids which help regulate the rate of transepidermal water loss and govern the hydration state of the skin.[1][9][10]

Cryogenic scanning electron microscopy has shown that lanolin, like human stratum corneum lipids, consists of a mass of liquid crystalline material. Cross-polarised light microscopy has shown the multilamellar vesicles formed by lanolin are identical to those formed by human stratum corneum lipids. The incorporation of bound water into the stratum corneum involves the formation of multilamellar vesicles.[1][10]

Skin bioengineering studies have shown the durational effect of the emollient (skin smoothing) action produced by lanolin is very significant and lasts for many hours. Lanolin applied to the skin at 2 mg/cm2 has been shown to reduce roughness by about 35% after one hour and 50% after two hours, with the overall effect lasting for considerably more than eight hours.[1] Lanolin is also known to form semiocclusive (breathable) films on the skin.[2] When applied daily at around 4 mg/cm2 for five consecutive days, the positive moisturising effects of lanolin were detectable until 72 hours after final application.[1] Lanolin may achieve some of its moisturising effects by forming a secondary moisture reservoir within the skin.[9][10]

The barrier repair properties of lanolin have been reported to be superior to those produced by both petrolatum and glycerin.[1] In a small clinical study conducted on volunteer subjects with terribly dry (xerotic) hands, lanolin was shown to be superior to petrolatum in reducing the signs and symptoms of dryness and scaling, cracks and abrasions, and pain and itch. In another study, a high purity grade of lanolin was found to be significantly superior to petrolatum in assisting the healing of superficial wounds.

Applications

Lanolin ointment

Lanolin and its many derivatives are used extensively in both the personal care (e.g., high value cosmetics, facial cosmetics, lip products) and health care sectors such as topical liniments. Lanolin is also found in lubricants, rust-preventative coatings, shoe polish, and other commercial products.[11]

Lanolin is a relatively common allergen and is often misunderstood as a wool allergy. However, allergy to a lanolin-containing product is difficult to pinpoint and often other products containing lanolin may be fine for use. Patch testing can be done if a lanolin allergy is suspected.[11]

It is frequently used in protective baby skin treatment and as a treatment for sore nipples in breastfeeding mothers.[12]

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. The water-repellent properties make it valuable as a lubricant grease where corrosion would otherwise be a problem.

Lanolin is often used as a raw material for producing cholecalciferol using irradiation. (vitamin D3).

Baseball players often use it to soften and break in their baseball gloves (shaving cream with lanolin is popularly used for this).

Anhydrous lanolin is also used as a lubricant for brass instrument tuning slides.

Lanolin can also be restored to woolen garments to make them water and dirt repellent, such as for cloth diaper covers.

Lanolin is also used in lip balm products such as Carmex. For some people, it can irritate the lips.

Lanolin is sometimes used by people on Continuous positive airway pressure therapy to reduce irritation with masks, particular nasal pillow masks that can often create sore spots in the nostrils.

Anhydrous liquid lanolin, combined with parabens, has been used in trials as artificial tears to treat dry eye.[13][14]

Lanolin is used as a primary lubricating component in aerosol based brass lubricants in the ammunition reloading process. Mixed warm 1:12 with highly concentrated alcohol (usually 99%), the alcohol acts as a carrier which evaporates quickly after application, leaving a fine film of lanolin behind to prevent brass seizing in resizing dies.

Lanolin, when mixed with ingredients such as neatsfoot oil, beeswax and glycerine (glycerol), is used in various leather treatments, for example in some saddle soaps and in leather care products.

Production

Crude lanolin constitutes about 5–25% of the weight of freshly shorn wool. The wool from one Merino sheep will produce about 250–300 ml 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 wax-like substance melting at approximately 38 °C (100 °F).

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 The Lanolin Book, Edited by Udo Hoppe, Published by Beiersdorf AG, Hamburg 1999
  2. 1 2 3 4 5 Barnett G (1986). "Lanolin and Derivatives". Cosmetics & Toiletries. 101: 21–44.
  3. ↑ Riemenschneider, W.; Bolt, H. M. (2005). "Esters, Organic". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a09_565.pub2. ISBN 3527306730.
  4. ↑ BASF website – Alkoxylation: Reaction of ammonia or amines with ethylene oxide or propylene oxide to produce aminoalcohols. The process is also adaptable to produce specialty aminoalcohols from other epoxides
  5. ↑ Meriam-Webster medical dictionary – quaternise: to convert (as an amine) into a quaternary compound
  6. ↑ Arden Jones MR, Steel I, Powell SM (July 2002). "British Contact Dermatitis Group: Summaries of Papers". British Journal of Dermatology. 147 (Suppl 62): 71. doi:10.1046/j.1365-2133.147.s62.19.x.
  7. 1 2 3 Steel I (December 1994). "Lanolin Allergy: Hype or Hypersensitivity?". Journal of the National Eczema Society (Exchange) (75): 16–17.
  8. ↑ Steel I, White IR and Beck, MH (1995) "Dilemmas in Lanolin Sensitivity", 10th International Symposium on Contact Dermatitis, Nagoya, Japan
  9. 1 2 EW Clark and I Steel, Poster No. 2, American Academy of Dermatology, Washington DC, 1993
  10. 1 2 3 Clark EW, Steel I (July–August 1993). "Investigations into biomechanisms of the moisturizing function of lanolin" (PDF). Journal of the Society of Cosmetic Chemists. 44: 181–195.
  11. 1 2 Zirwas, M. J.; Stechschulte, S. A. (2008). "Moisturizer allergy: Diagnosis and management". The Journal of clinical and aesthetic dermatology. 1 (4): 38–44. PMC 3016930Freely accessible. PMID 21212847.
  12. ↑ HPA® Lanolin Cream. lansinoh.com
  13. ↑ Wang IJ, Lin IC, Hou YC, Hu FR (2007). "A comparison of the effect of carbomer-, cellulose- and mineral oil-based artificial tear formulations". Eur J Ophthalmol. 17 (2): 151–159. PMID 17415686.
  14. ↑ Pucker AD, Ng SM, Nichols JJ (2016). "Over the counter (OTC) artificial tear drops for dry eye syndrome". Cochrane Database Syst Rev. 2: CD009729. doi:10.1002/14651858.CD009729.pub2. PMC 5045033Freely accessible. PMID 26905373.

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