Sebum's chemical properties are primarily determined by its composition, which is a complex mixture of lipids.
Sebum Composition
According to research, human sebum found within the sebaceous gland lumen consists of the following major components [Downing et al., 1969]:
- Triglycerides: 57%
- Wax Monoesters: 25%
- Squalene: 13%
- Cholesterol Esters: 3%
- Cholesterol: 2%
Chemical Properties Explained
These components give sebum its distinct chemical properties:
- Lipid-Rich: Sebum is predominantly composed of lipids, making it hydrophobic (water-repelling). This is due to the high percentage of triglycerides, wax monoesters, and squalene.
- Viscous Nature: The mixture of these lipids results in a viscous, oily substance that is important for skin lubrication and protection.
- Non-Polar Characteristics: Due to the high proportion of non-polar lipids like squalene and triglycerides, sebum is highly non-polar, which means it does not mix with water easily.
- Stability: The presence of wax esters contributes to sebum's stability and resistance to degradation.
- Specific Fatty Acid Composition: Although not detailed in the provided reference, the specific types of fatty acids within the triglycerides and wax esters are unique to each species, resulting in varying sebum compositions [Lindholm et al., 1981].
Practical Insights
- Skin Barrier Function: Sebum plays a crucial role in maintaining the skin's protective barrier, preventing water loss, and shielding against external pathogens.
- Skin Hydration: By forming an oily layer on the skin, sebum helps to trap moisture and keep the skin hydrated.
- Acne Development: Overproduction of sebum, combined with skin cell debris, can clog pores, leading to acne.
- Variability: The composition and thus the properties of sebum are species-specific.
Summary
The chemical properties of sebum, characterized by its lipid-rich, viscous, and hydrophobic nature, are a result of its unique composition, primarily triglycerides, wax monoesters, squalene, and cholesterol compounds. These properties are crucial for its function as a skin protectant and lubricant.
