Details
The famous Vaseline or Petroleum Jelly. Just like mineral oil, it is also a by-product of refining crude oil, aka petroleum, and it is also a mixture of hydrocarbons but with bigger (C18-90+) carbon chain length.
The unique thing about petrolatum is that it is the most effective occlusive agent known today. While the occlusivity of mineral oil is in the same league as the occlusivity of plant oils, petrolatum is in a league of its own. It sits on top of the skin and hinders so-called transepidermal water loss (TEWL) like nothing else.
This comes in handy healing cracked lips or severely dry skin patches, though overdoing it (i.e. reducing TEWL by more than 40%) is not good as it can create a nice moist place for fungi and bacteria to grow.
As for petrolatum and safety, we can write here pretty much the exact same thing as we have written at mineral oil. There is no evidence whatsoever that cosmetic, USP grade petrolatum is carcinogenic. It also does not absorb into the skin but sits on top of it and that in itself greatly minimises health risks. It also has a long history of safe use, as it was first used as a skincare product more than 100 years ago, in 1872 to be precise.
It is also non-comedogenic, though its pure form is very heavy and greasy so combination and oily skin types might want to avoid it anyway.
Overall, it is the gold-standard occlusive agent known today and a tub of Vaseline comes in handy in any household to heal cracked lips or other severely dry skin patches.
Show me some proof
- Petry, T., et al. "Review of data on the dermal penetration of mineral oils and waxes used in cosmetic applications." Toxicology Letters 280 (2017): 70-78.
- Leslie Baumann, MD, Cosmetic Dermatology, 2nd edition, Occlusives - pages 273-274
- Rawlings, A. V., and K. J. Lombard. "A review on the extensive skin benefits of mineral oil." International journal of cosmetic science 34.6 (2012): 511-518.