petroleum jelly
Meaning of petroleum jelly: A greasy blend of mineral waxes and oils that seals water into the skin rather than adding any moisture itself.
Definition of petroleum jelly
Petroleum jelly is a semi-solid blend of mineral oils and waxes obtained from crude oil and then purified. It has no smell or taste and does not dissolve in water. Spread on skin it forms a barrier that slows the escape of water from the surface, which is why dry, cracked or healing skin becomes softer beneath it.
How does it help skin?
It works by blocking evaporation rather than by supplying anything. Skin holds water in its outer layer, and that layer loses water constantly to the air. A film of petrolatum cuts that loss dramatically, so water arriving from below stays where it is useful and the surface softens. Applying it to damp skin therefore achieves more than applying it to dry skin. It also keeps a healing wound moist, and a moist wound forms less of a hard scab, which is why it is spread on grazes and on the raw area left after a skin graft is taken. The jelly itself does not heal anything. It creates the conditions in which the skin heals.
What else is it used for?
| Use | What it is doing |
|---|---|
| Ointment base | Carrying an active drug and holding it against the skin |
| Barrier on skin exposed to urine or stool | Keeping irritants off the surface |
| Chapped lips and dry nostrils | Sealing in water where skin is thin |
| Protecting surrounding skin during treatment | Shielding healthy areas from a caustic product |
| Reducing friction | Preventing rubbing between skin surfaces |
What should be known about it?
The refined grade used in medicine and cosmetics has had the tarry byproducts of crude oil removed, and the unrefined material is a different substance with a different safety profile. Refined jelly sits on the surface and is not absorbed to any meaningful degree. It does not block pores in most people, despite a persistent belief that it does. Two genuine cautions exist. Being oil based, it weakens latex, so condoms and diaphragms lose reliability on contact with it. Repeated use inside the nose has been linked to a form of lung inflammation when droplets are inhaled over long periods, reported mainly in children and older adults.
Also known as
Used in a sentence
Petroleum jelly was applied to the donor site to stop the dressing adhering to the wound.
Good to know
Petroleum jelly seals in water rather than supplying it, so it does most on skin that is already damp, and because it is oil based it weakens latex condoms and diaphragms.
Word origin
Where “petroleum jelly” comes from
Petroleum comes from the Latin petra, meaning rock, and oleum, meaning oil, so the name reads as rock oil.