Mineral oil is a colorless and odorless liquid created as a by-product of making gasoline. It’s commonly added to skin care and hair care products as a moisturizing agent because it’s cheap to manufacture. According to dermatologist Ava Shamban, “creams that combine mineral oil and paraffin can actually damage the skin barrier and increase water loss.” Oils used in hair care products are hydrophobic Trusted Source, meaning they repel water. Applying mineral oil to your hair may reduce the amount of water your hair absorbs and minimize swelling. Repeated swelling and drying can damage your hair.

“I highly recommend staying away from mineral oil,” says Beverly Hills aesthetician Sonya Dakar, whose clients include Jennifer Lawrence and Gwyneth Paltrow. “It’s derived from petroleum and does not absorb into the skin—its molecular size is simply too big. As a result, mineral oil remains on the surface of skin, making it a reflector of the sun, which can lead to more sun damage and discoloration.” And while there are many oils that can moisturize without clogging pores, mineral oil isn’t one of them. “It’s the one type of oil I don’t recommend for any skin types,” says Dallas-based celebrity aesthetician Renée Rouleau. “It clogs the pores and suffocates the skin. Cosmetic companies formulate moisturizers with heavy oils, such as mineral oil or petroleum, to replenish dry skin. But those oils have large molecular structures, so they usually never truly penetrate. Your moisturizer should always absorb into the skin, not just sit on the surface.”

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4387693/