What it is
Mineral oil is a highly refined mixture of saturated hydrocarbons derived from petroleum and purified to cosmetic grade. In sunscreens it serves as an emollient that gives slip and a smooth feel, and as an occlusive that forms a light surface film to reduce transepidermal water loss. It is chemically inert, odorless, and resistant to oxidation, which makes it a stable carrier and texture agent.
Safety & warnings
Cosmetic-grade mineral oil is well tolerated and considered non-sensitizing for most people, and refined grades are non-irritating. It can be comedogenic for some acne-prone users because its occlusive film may trap debris, though highly refined cosmetic grades are generally low on practical comedogenicity scales; people prone to clogged pores may prefer to monitor how their skin responds.
Origin & sourcing
Petroleum-derived; crude oil fractions are distilled and then extensively refined and purified to remove aromatic and reactive components, yielding a cosmetic- or pharmaceutical-grade oil.
Questions everyone asks
Why is mineral oil in sunscreen?
It works as an emollient and occlusive, giving the product slip and a smooth finish while forming a light film that helps limit water loss from the skin.
Will mineral oil clog pores?
Highly refined cosmetic-grade mineral oil is generally low risk, but because it is occlusive some acne-prone people find it can contribute to clogged pores, so it is worth watching how your skin reacts.