Wool grease is a thick, waxy substance naturally harvested from the fleece of domestic sheep. This material, sometimes called wool wax or wool yolk, is the raw form of lanolin, one of the oldest and most widely used ingredients in consumer products. The substance is collected after the sheep are shorn for fiber.
The Origin and Function of Raw Wool Grease
Raw wool grease originates from the sebaceous glands in the skin of wool-bearing sheep. This waxy secretion mixes within the fleece with suint, the water-soluble portion of the sheep’s sweat. The resulting mixture of grease, suint, and debris is often called “yolk” while embedded in the shorn wool.
The primary biological role of the grease is to protect the animal from harsh environmental conditions. It coats the wool fibers, making the fleece highly water-resistant and helping the sheep shed moisture. This coating also acts as a moisturizer, maintaining the elasticity and flexibility of the wool fiber and the sheep’s skin.
The Transformation Process into Lanolin
The industrial conversion of raw wool grease begins with wool scouring. Shorn wool is washed in a hot, aqueous solution containing specialized detergents to separate the grease and dirt from the fibers. This washing liquid contains the crude wool grease, along with other impurities.
The next stage isolates the grease from the wash water, typically through gravity settlement followed by high-speed centrifugation. Centrifugal force separates the lighter wool grease concentrate from the heavier water and solid contaminants. The resulting crude wool grease requires extensive refinement to become pharmaceutical-grade lanolin.
Further purification steps remove remaining impurities such as soaps, residual pesticides, and odors. This is achieved through techniques like filtration, neutralization of free fatty acids with alkaline treatments, and bleaching. The final product is anhydrous lanolin, which is purified, water-free wool grease suitable for human use.
Primary Applications in Health and Cosmetics
Lanolin is valued for its moisturizing and protective capabilities in consumer goods. It functions as an occlusive moisturizer, creating a semi-permeable barrier on the skin’s surface that prevents water from evaporating. This barrier effect can reduce transepidermal water loss by a significant margin.
Lanolin is a common ingredient in many daily-use items, including heavy-duty hand creams, lip balms, and specialized dry skin lotions. Its soothing and protective qualities make it a staple in products addressing irritation, such as diaper rash creams for infants. Ultra-purified lanolin is also frequently used in nipple creams for breastfeeding mothers to soothe and protect sore skin.
In topical medications, lanolin serves as an excellent base for delivering active ingredients due to its compatibility with the skin’s natural lipids. Its ability to soften and smooth dry, flaky skin also makes it beneficial in products aimed at wound healing and managing minor abrasions.
Unique Chemical Composition and Properties
Lanolin is classified chemically as a wax because it lacks the glycerides found in true fats. It is an extremely complex mixture, consisting predominantly of waxy esters, which can account for up to 97% of its weight. The remaining composition includes high molecular weight lanolin alcohols and fatty acids.
The structure of lanolin contains a diverse array of molecules, with thousands of different ester combinations possible from hundreds of distinct alcohols and acids. This unique chemical complexity gives lanolin its characteristic high viscosity and stability. A notable property is its capacity to absorb a large volume of water, often up to twice its own weight, which is critical to its function as a skin emollient.