“Slugging”: sealing your skin overnight, explained

“Slugging” sounds like something you’d rather not do to your face. The name comes from the glossy, slightly slimy look of skin coated in an ointment overnight. The idea behind it is old and solid, though: seal the skin so less water escapes while you sleep. Here’s what the science says, who it suits, and where it can go wrong.

What slugging actually is

Slugging means applying a thin layer of an occlusive ingredient, most often petrolatum (petroleum jelly), as the very last step of your evening routine. You go to bed shiny and, ideally, wake up with softer, less tight skin.

A 2022 editorial in the dermatology journal Cutis noted how much social media attention the trend brought to petrolatum, a product dermatologists have used for generations. The trend is new; the ingredient and the principle are not.

How occlusion works

Your skin constantly loses a little water through its outer layer, the stratum corneum. Researchers measure this as transepidermal water loss, or TEWL. When the barrier is dry or damaged, more water escapes and the skin feels tight, rough or itchy.

An occlusive is an ingredient that forms a water-resistant film on the skin and slows that evaporation. It doesn’t add water. It keeps in the water that’s already there.

Petrolatum is the most effective occlusive in common use. According to the Cutis editorial, it reduces water loss by about 98%, while other oil-based moisturizers manage about 20% to 30%.

It’s more than plastic wrap

You might picture petrolatum as a sheet sitting on top of the skin. A classic 1992 study found something more interesting. After researchers damaged the skin barrier of volunteers, petrolatum sped up barrier recovery rather than slowing it. Under the microscope, the petrolatum had spread into the spaces between cells at every level of the stratum corneum, filling in among the natural lipids.

A 2016 study went further. In 36 healthy people and 13 people with moderate atopic dermatitis (eczema), skin covered with petrolatum showed higher levels of the skin’s own germ-fighting proteins and of barrier proteins such as filaggrin, compared with skin that was only covered. It was a small study looking at molecules rather than symptoms, but it suggests petrolatum is less “inert” than its reputation.

Who slugging suits

Slugging makes the most sense when your skin is losing water faster than it can keep up:

• Dry, flaky or tight skin, especially in a Canadian winter with the furnace running
• Chapped, irritated patches, such as around the nose after a cold, or cracked hands and heels
• Sensitive thin skin like lips and eyelids, where the Cutis editorial notes petrolatum is less irritating than lotions
• Eczema-prone skin between flares, as part of a routine your doctor has agreed on

It works best on damp skin. Dermatologists have long used a “soak and smear” technique: soak the skin in plain water, then immediately apply petrolatum to lock the water in. A gentler everyday version is to apply your usual moisturizer to slightly damp skin, then a thin layer of occlusive on top. A plain ointment or balm does the job.

The editorial is clear that petrolatum alone works when there isn’t much inflammation. Red, inflamed or very severe eczema may need a prescription treatment. If your skin isn’t improving after two weeks of gentle care, see your doctor or pharmacist.

When slugging can backfire

Acne-prone skin

Here the evidence is mixed in a useful way. A 2024 review in the Journal of the American Academy of Dermatology lists “petrolatum causes acne” among the misconceptions about it. At the same time, the American Academy of Dermatology advises people with acne to use gentle products and choose ones labelled non-comedogenic (tested not to clog pores). Oils and other ingredients in whatever you put under the petrolatum still matter.

If you break out easily, a sensible approach is to slug only the dry spots, not your whole face, or to skip it and use a lighter moisturizer instead.

Over active treatments

Occlusion tends to increase how much of whatever is underneath gets absorbed, according to a 2002 review. That’s useful when your doctor prescribes a medicated ointment, but it can backfire with things that are already irritating, such as retinoids (vitamin A creams), exfoliating acids or benzoyl peroxide. Sealing them in can make stinging and peeling worse. Slug on nights you skip those products, unless a doctor or pharmacist tells you otherwise.

Too much, for too long

The same 2002 review points out that occlusion raises the water content of the outer skin layer, and long, continuous occlusion can actually compromise barrier function. A thin layer overnight is very different from skin that’s sealed around the clock for days, but it’s a reason to think of slugging as a tool for dry spells, not a permanent routine for everyone.

A few practical points:

• Use a thin layer. More isn’t better, and it ends up on your pillowcase.
• Wash your pillowcase more often while you’re slugging.
• Wash your face gently in the morning.
• Skip it on infected or weeping skin; that needs a doctor’s look.

What slugging can’t do

It’s worth keeping expectations realistic:

• It doesn’t add water. It only keeps in what’s there, which is why applying it to damp skin or over a moisturizer helps.
• It doesn’t treat inflammation. Eczema flares, rosacea and dermatitis need proper treatment.
• It won’t erase wrinkles. Plumper, better-hydrated skin can look smoother overnight, but that’s hydration, not a structural change.
• It isn’t a substitute for sunscreen or for the rest of a gentle routine.

Slugging is simply occlusion with a catchy name. A thin layer of petrolatum over damp or moisturized skin slows water loss dramatically, and research suggests it helps the barrier recover rather than just sitting on top. It’s a great fit for dry, chapped or winter-worn skin, less so for acne-prone faces, and it’s best kept away from retinoids and acids. Use it when your skin needs it, keep it thin, and see your doctor if dryness comes with redness or inflammation that doesn’t settle.