Mineral oil is a clear, colorless, odorless, petroleum derivative. It's chemically similar to petroleum jelly and is produced in heavy and light grades, or viscosities. There are three further classifications — paraffinic, aromatic, and naphthenic — based on what type of alkanes the oil is made from, and they have slightly different chemical makeups and properties. Inexpensive and easy to make, it's used in many different products, including cooling systems, lubricants, cosmetics, and medicine.
A variety of cosmetics contain mineral oil, including popular skin care products like cold cream as well as medical ointments for adults, children, and babies. In a purified, semisolid form called liquid petrolatum, it is often used as a base for salves, protective dressings, and skin softeners. It is widely believed to be one of the most effective moisturizers available.
Many people have expressed concern about the role of this oil in cosmetics, particularly that it may "block" the skin and prevent toxins from escaping. Most researchers believe that very few toxins are expressed from the body through the skin, however. Unlike some other skin care additives, research suggests that the refined type of oil used in cosmetics does not clog pores and is generally considered safe for all types of skin. People who have naturally oily skin may want to avoid items that contain it, since it can make the skin feel even more greasy.
There are also concerns that this oil could contain damaging impurities. The very refined oil that's used in personal products is not the same as that used for industrial purposes, however, and does not contain the same impurities. There may be some legitimate concern that petrolatum (another name for mineral oil jelly) and liquid paraffin may make the skin more sensitive to the sun, so people who use products that contain it should be careful to monitor their sun exposure.
Industrial and Scientific Uses
Two properties of mineral oil make it popular for use with industrial and electrical components: it doesn't conduct electricity and it is a poor conductor of heat, and it takes the place of air and water where it's applied, so it can keep parts from corroding. As such, some varieties are used on tools, machines, and even the metallic surface and components of ships to keep them from rusting. It also resists compression, so it's commonly used to provide resistance in hydraulic assemblies.
In addition to its industrial uses, mineral oil prevents the absorption of moisture from the atmosphere, so it works well as a preservative for lithium and other alkali metals. These elements react when exposed to the atmosphere, tarnishing quickly or even catching on fire or exploding, depending on the metal. Some labs also use this substance to make an overlay for cultures in petri dishes.
Wooden utensils, cookware and food preparation tools like cutting boards can benefit from this oil's water repellent properties too. Since it's nearly odorless and tasteless, highly refined, food-grade oils can be used to keep the wood from cracking and accumulating bacteria without contributing unwanted flavor or odor to foods. Some people also use it to grease pans before baking or frying. Because industrial grade oil can contain toxic impurities, cooks should only use oil that is clearly labeled as being safe for use in the kitchen.
Marketed as early as the 19th century under the trade name Nujol, mineral oil has a long history as a treatment for constipation. When swallowed in small amounts, it acts as an internal lubricant and prevents the large intestine from absorbing water. This also prevents the absorption of some types of nutrients, so it can cause nutritional problems if abused.
A few drops of warm — not hot — oil can also be used to help soften ear wax. When followed by a gentle water or hydrogen peroxide irrigation, it can help remove any excess wax buildup in the ear canal.
Effects of Exposure
While most people can use mineral oil without any harmful effects, some people do have allergic reactions to it, including hives, trouble breathing, swelling of the face, and tightness of the chest. Anyone with these symptoms should seek medical care promptly, since they can be dangerous. Though there have been concerns about high viscosity oils being used as additives in food, they are considered to be generally safe when consumed in moderate amounts by government agencies, including the Food and Drug Administration (FDA) and the European Food Safety Authority (EFSA).
Exposure to aerosol forms of this substance is an occupational hazard for some workers. It's a respiratory irritant when in mist form, and people who have impaired lung function can have their condition worsen when they're exposed to it. Similarly, those with pre-existing skin disorders are more likely to develop inflammation on contact. The risk of exposure to high-concentration mists is a regulated occupational hazard that is subject to workplace monitoring in many countries.