Squalane is a saturated form of squalene in which the double bonds have been eliminated by hydrogenation. Because it is less susceptible to oxidation, it is more commonly used in personal care products than squalene.
Squalene is the biochemical precursor to the whole family of steroids. Oxidation (via squalene monooxygenase) of one of the terminal double bonds of squalene yields 2,3-squalene oxide, which undergoes enzyme-catalyzed cyclization to afford lanosterol, which is then elaborated into cholesterol and other steroids.
Squalene is a low density compound often stored in the bodies of cartilaginous fishes such as sharks, which lack a swim bladder and must therefore reduce their body density with fats and oils. Squalene, which is stored mainly in the shark's liver, is lighter than water with a specific gravity of 0.855. Environmental and other concerns over shark hunting have motivated its extraction from vegetable sources instead.
Recently it has become a trend for sharks to be hunted to process their livers for the purpose of making squalene health capsules. However, there is little clinical evidence to prove that, taken internally, squalene does anything to increase an individual's quality of life.
A study linking squalene, as experimental vaccine adjuvant, to individuals with the clinical signs of Gulf War syndrome was published in 2002. The published findings strongly suggest that the squalene contaminated vaccines could be responsible for the Gulf War Syndrome symptoms seen in the study group, and recommended that a large scale epidemiological study be performed to verify or correct this. Despite repeated assurances that the vaccine was safe and necessary, a U.S. Federal Judge ruled that there was good cause to believe it was harmful, and he ordered the Pentagon to stop administering it in October 2004.
Squalene is used in cosmetics as a natural moisturizer. It penetrates the skin quickly, does not leave a greasy feeling on the skin and blends well with other oils and vitamins.