Squalene is a naturally occurring lipid produced in the human sebaceous glands and secreted as a component of skin surface lipids. In young skin, it constitutes approximately 12 to 15 percent of sebum by weight — the highest concentration of any individual lipid in human sebum. It functions as an emollient, an antioxidant, and a precursor to cholesterol synthesis in the epidermis.
It is also almost never used in skincare formulations. The reason is oxidative instability.
The Oxidation Problem
Squalene is a triterpene hydrocarbon — a 30-carbon molecule with six double bonds. These double bonds are the source of its biological activity and also its chemical vulnerability. In the presence of atmospheric oxygen, UV radiation, or other oxidative stressors, squalene undergoes peroxidation at its double bonds, forming squalene peroxides and aldehydes.
Squalene peroxidation is significant not only because it destroys the compound's beneficial properties, but because the peroxidation products are themselves bioactive — and not beneficially. Squalene monohydroperoxide, the primary initial peroxidation product, has been demonstrated to be comedogenic and pro-inflammatory, contributing to the microcomedone formation that initiates acne lesions.
Hydrogenation: What It Solves and What It Changes
Squalane is squalene with all six double bonds hydrogenated — saturated. The resulting molecule is chemically identical to squalene except for the absence of the double bonds, which renders it resistant to oxidative degradation. Squalane has a shelf life measured in years without antioxidant stabilisation.
What hydrogenation changes is molecular geometry. Squalene's double bonds introduce angular kinks into the molecule that influence how it interacts with other lipid structures. Squalane, fully saturated, adopts a more linear configuration. Whether this geometric difference is biologically meaningful is not definitively resolved in the published literature.
The available evidence suggests that squalane retains most of squalene's emollient and occlusive properties. The antioxidant properties of squalene — which may be relevant in the context of sebum's protective function — are substantially diminished in the saturated form.
Source Considerations: Shark vs. Olive vs. Sugarcane
Historically, squalene was extracted from the liver oil of deep-sea sharks — a sustainable sourcing concern that drove regulatory and consumer pressure toward plant-derived alternatives.
Modern cosmetic squalane is derived predominantly from olive oil or from sugarcane fermentation. Both sources are functionally equivalent as finished squalane — the hydrogenation step produces the same molecule regardless of origin. The sugarcane fermentation route produces a higher-purity squalane with more consistent molecular weight distribution than olive-derived squalane, and at lower cost.
The Stability Conclusion
The decision to use squalane over squalene in skincare formulations is the correct one given current formulation science. The oxidation liability of squalene is not manageable without antioxidant systems that would significantly complicate formulation and reduce stability certainty.
The biological cost of hydrogenation — the loss of antioxidant activity and possible reduction in receptor affinity — is real but smaller than the formulation benefit of stability. For now, squalane is the appropriate surrogate: not perfect, but structurally close, functionally adequate, and manufacturable.
YlemosPure Journal — J-006 / Lipid Chemistry / April 2024