The ones that can do that—meaning your skin feels soft, hydrated, and supple all day long—usually contain omega fatty acids.

The best fatty acids for essential fatty acids omega 3 (linolenic acid) and 6 (linoleic acid) and essential omega 9 (oleic acid). The first two—essential fatty acids—are often called vitamin F. (The name is a little confusing because they’re not true vitamins.) Together, linolenic and linoleic acids create a natural seal on the skin—delight. of water and nutrients beneath it.

“These fatty acids are part of the seal that sits in the cracks between the cells in the outer layer of the skin,” board-certified dermatologist Joshua Zeichner, MD, tells us about fatty acids. Simply put, he explains, they’re like the grout that sits between the tiles in a bathroom. “Natural fats maintain the integrity of the outer layer of the skin,” he says. Essentially, these fatty acids help your skin barrier do its job.

You can find omega fatty acids in many skin care products, such as lotions, face creams, and even serums. But they work especially well in oils because they complement the intended purpose of the oil, which, as I mentioned earlier, is to create a comfortable seal against the skin. Face and body oils are always the last step in skin care for a reason: they’re occlusive. Products with occlusive properties retain moisture and nutrients from below.