petrolatum
Meaning of petrolatum: A semi-solid jelly refined from crude oil that seals water into skin without supplying any of its own.
Definition of petrolatum
Petrolatum is a soft, semi-solid mixture of hydrocarbons refined from petroleum, supplied as a translucent jelly with no smell or taste. Spread on skin it forms a film that blocks water from evaporating, which places it in the group of moisturizers called occlusives. It also serves as the base into which many ointment medicines are mixed.
How does it help skin?
Skin holds water in because of an outer layer of dead flattened cells packed with lipid between them, a structure often compared to bricks and mortar. When that mortar is disrupted by cold, detergents, repeated washing or eczema, water escapes and the surface cracks. Petrolatum fills the gaps and seals the surface. It does not add water and it does not repair the barrier, but by cutting evaporation to a fraction it gives the skin below time to restore itself.
| Type of moisturizer | How it acts |
|---|---|
| Occlusive, such as petrolatum | Blocks water leaving the surface |
| Humectant | Draws water into the outer layer |
| Emollient | Fills gaps between surface cells and smooths them |
What is it used on?
Dry and cracked skin, chapped lips, minor grazes and burns once cleaned, skin around a stoma or a wound where discharge would otherwise cause damage, and the inside of the nostrils when they are dry. It is used to protect skin during radiation treatment and to occlude a medicated ointment. Mixed with other ingredients it appears in combinations such as petrolatum, mineral oil, lanolin and ceresin ointment, where each component adjusts the texture and staying power.
What is worth knowing about it?
Grades used in medicines and cosmetics are refined to remove the aromatic compounds present in crude petroleum, and the purified product does not penetrate beyond the outer layer of skin. Two practical issues recur. It is greasy, stains fabric and takes time to absorb, which is why creams are often preferred for daytime use despite being less effective at sealing. And when it is applied repeatedly inside the nose, small amounts can be inhaled over time and settle in the lung, producing the slow inflammation called lipoid pneumonia, a risk that falls mainly on the very young and the very old. It is the same substance as petroleum jelly, which is simply the everyday name for it.
Also known as
Used in a sentence
Petrolatum was applied to the treated area to protect the skin during the radiation course.
Good to know
Petrolatum seals water in rather than supplying it, so it works on damp skin and does nothing to repair the barrier itself.
Word origin
Where “petrolatum” comes from
From the Latin petra, meaning rock, and oleum, meaning oil, recording that the material is drawn from the ground.