When looking for someone to take skincare advice from, you might want to consider Lisa Leslie. Her face is her resumé—not a pore, zit, or wrinkle to be seen. A year ago, the former WNBA star told us her secret, “Pond’s, Vaseline, and coconut oil are key,” she said.

Wait—what? VASELINE, in this day and age? (We'll save the great coconut oil debate for another day.)

Nearly 150 years after it was discovered, petroleum jelly's utility in skincare remains a point of contention. (Petroleum jelly is of course the generic name for Vaseline.) While originally marketed to heal wounds, petroleum jelly doesn’t actually have any healing or nourishing properties on its own—at least from a chemical perspective. However, it can protect wounds physically, by creating a barrier on skin, which in turn prevents moisture from escaping. Moisture is key to helping skin heal—by not allowing it to dry, petroleum jelly stops cuts and wounds from getting irritated and scabbing. Think of how a Band-Aid physically protects and blocks the skin so it can heal—it’s like that. On the other hand, that barrier also traps any bad bacteria that may already be on the skin. “Acne and rosacea can be worsened by a thick emollient,” dermatologist Dr. Patricia Wexler notes, while dry skin can be made drier when blocked off from moisture in the air. “It can cause breakouts if put over unwashed skin, and is difficult to wash off even with soap.”

Underneath the surface, petroleum jelly is more or less the refined byproduct of crude oil—a blend of mineral oil and waxes. And there lies both the good news and bad. Because it’s derived from the earth, petroleum jelly is technically 100-percent natural, but since that earth is really just fossil fuels, that means petroleum jelly is neither sustainable nor eco-friendly. And then there’s the matter of putting it on your skin. The concern there is that some of the cancer-causing chemicals found in crude oil may contaminate the petroleum jelly. Vaseline (name brand) uses a triple-process refinement but Dr. Wexler warns, “There are many Vaseline imitators, made by smaller companies, and one doesn't always know the extent of processing done.” To play it safe, you may want to stock up on petroleum-based products next time you’re at City Pharma—in Europe, petroleum jelly can only be used in skincare and cosmetics “if the full refining history is known and it can be shown that the substance from which it is produced is not a carcinogen.”¹

Petroleum jelly is still a popular ingredient in moisturizers because it’s practically unmatched in occlusiveness (yes, we’re back to the skin barrier-protecting point). Vaseline is 100-percent petroleum jelly, while Aquaphor adds glycerin for a bit more moisture, and Homeoplasmine works with the waxier form, paraffin. Crème de La Mer, Elizabeth Arden Eight Hour Cream, and CeraVe all derive their occlusive properties from petroleum jelly, too. As for mineral oil? Dr. Wexler says petroleum jelly’s liquid sister is “an inert, chemically stable ingredient that is, for the most part, non-comedogenic, good for sensitive skin, and unlikely to cause an allergic reaction.” In the beauty aisle, Embryolisse and… pretty much all of the other French pharmacy brands are chock full of it (including Avène, La Roche-Posay, Bioderma, and Mustela, which makes us wonder if the secret to French girl skin just a fossil fuel byproduct after all.)

So: should you slather it all over your face? Probably not. Is it bad? Well, Dr. Wexler still recommends it for skin that’s injured or cracking, and it can’t hurt to throw some in your bag. But, she does mention, “hydrocarbon based products are slowly being substituted with eco-friendly sustainable alternatives.” Soon the old staple may be just that—a thing of the past.

This article has been updated since its original publish date. Ashley Smith (The Society) photographed by Tom Newton.