Squalene

Squalene is a very non-polar, naturally found liquid compound.

It is a hydrocarbon (meaning that it only contains carbon and hydrogen atoms) with multiple unsaturated double bonds and is a part of the natural metabolism of all plants and animals. It is different from squalane, which is a fully saturated version of squalene with no double bonds.

It is used by the human body as a building block for the synthesis of cholesterol and steroid hormones. It is one of the main ingredients in the sebum, the oily substance produced by the skin. Sebum contains approximately 12% of squalene, along with triglycerides, free fatty acids, and waxes.

Squalene is added to moisturizers to help rebuild the natural oily film on the skin’s surface and to prevent transdermal water loss. The addition of squalene helps to mimic the natural composition of human sebum and to restore the natural balance on the skin’s surface.

It can protect against UV light, and, due to its unsaturated double bonds, it is also an antioxidant that can protect the skin cells from oxidative damage. The research focused on the additional roles of squalene in skin protection is still ongoing.

In the past, the main source of squalene for cosmetic and medical purposes was shark liver (this is also how squalane got its name – Squalus is a Latin name for dogfish sharks). Shark liver contains more than 40% of squalene, but shark hunting must be properly regulated in order to be sustainable (although the sustainability of shark hunting in the first place can be argued).

Alternative sources from vegetables and its biosynthetic production are used these days. These include plant oils, such as olive and peanut oil. Unfortunately, these oils only contain minor amounts of squalene (less than 1%).

Squalene is listed among common comedogenic ingredients by acne.org.