Petrolatum
Petrolatum, also known as petroleum jelly or Vaseline, is a semi-solid mixture of hydrocarbons derived as a by-product of refining crude oil, with carbon chain lengths ranging from C18 to C90+. It is listed under CosIng with antistatic and emollient functions, and carries a cosmetic restriction (II/904) unless the full refining history is known and carcinogenicity can be excluded. It does not absorb into the skin but sits on top of it, forming a physical barrier.
Petrolatum is considered the most effective occlusive agent known, reducing transepidermal water loss (TEWL) more effectively than mineral oils or plant oils. It is particularly useful for healing cracked lips and severely dry skin patches. It has a long history of safe use dating back to 1872, and cosmetic/USP-grade petrolatum has no evidence of carcinogenicity.
Reducing TEWL by more than 40% is noted as potentially problematic, as it can create a moist environment conducive to fungal and bacterial growth. The cosmetic restriction II/904 applies unless the full refining history is known and the source material is confirmed non-carcinogenic. Its pure form is very heavy and greasy, so those with combination or oily skin may want to avoid it.
