Slugging: Does Sealing Your Face in Petroleum Jelly Actually Work?

Slugging is the practice of applying a generous layer of petroleum jelly — or a similar thick occlusive — as the final step of your evening skincare routine. The name comes from the appearance: the face, coated and gleaming, looks not unlike a slug. It became a proper trend via skincare communities on Reddit and TikTok, where users with dry or compromised skin reported waking up to soft, plumped, dramatically improved skin after a single night.

The mechanism behind it is not complicated, and the evidence for it — in the right context — is reasonably solid. The controversy is mostly about who should be doing it.

What slugging actually does

Petroleum jelly is an occlusive. It does not moisturise skin. It does not add water. What it does is form a physical barrier on the surface of the skin that dramatically slows transepidermal water loss — the process by which water evaporates from skin into the air.

If you have applied hydrating products beneath it — serums, essences, moisturisers — the occlusive layer keeps them in contact with the skin for longer, allowing them to do their work rather than evaporating away. This is why order matters: slugging over bare, dry skin locks in dryness. Slugging over well-hydrated skin locks in the hydration.

The concept is not new. Occlusives have been a staple of dermatology for decades, used in wound healing and the management of conditions like eczema and psoriasis. Petroleum jelly in particular is hypoallergenic, fragrance-free, and extraordinarily inert — it does not react with the skin, does not break down, and has one of the longest safety records of any topical ingredient in common use.

What TikTok discovered, in other words, is not a trick. It is a legitimate skincare principle that dermatology has known about for a long time.

Who genuinely benefits

Slugging makes the most sense for people with very dry or dehydrated skin, particularly during colder months when central heating and low humidity accelerate water loss. If your skin feels tight, flaky, or rough after cleansing even with a moisturiser applied, you have compromised barrier function — and an occlusive layer overnight will, for many people, produce a noticeable improvement.

People with eczema-prone or sensitised skin frequently use occlusive layering as part of their management routine, often on the recommendation of a dermatologist. For those already familiar with the concept, slugging as a trend is simply that practice by a different name.

Cold, dry climates and winter conditions are the other natural recommendation. The faster water evaporates from your skin — and it evaporates faster when the air is dry and temperatures are low — the more an occlusive layer does to slow the process overnight.

Who should skip it

Oily and acne-prone skin is where the advice changes significantly.

Petroleum jelly is non-comedogenic in the classical sense — it does not chemically clog pores. But its occlusive effect is indiscriminate. It traps everything: water, yes, but also sebum, shed skin cells, and, if your skin is breaking out, the conditions that make breakouts worse. For skin that is already producing excess oil or dealing with active acne, applying a thick occlusive layer overnight can trap the wrong things and worsen congestion.

The Reddit communities where slugging took off were largely dry-skinned. The trend sometimes lost that context when it spread to broader audiences, which is probably why the response to it has been so inconsistent — genuinely transformative for some, genuinely problematic for others.

Combination skin is, as always, the awkward middle case. Slugging on the cheeks and dry areas while avoiding the T-zone is an option, but it requires some application precision.

There is also the question of active ingredients. Slugging over retinoids or strong chemical exfoliants can increase absorption and, with it, the risk of irritation. If you use tretinoin or glycolic acid at night, slug on a different night or not at all.

How to do it correctly

If your skin type is appropriate for it, the protocol is simple:

1. Cleanse thoroughly. You are sealing in whatever is on your skin. That needs to be cleanser and nothing you would not want sitting there for eight hours.
2. Apply your hydrating products as usual — your toner, serum, moisturiser. Let them absorb for a few minutes.
3. Apply a small amount of petroleum jelly as the final layer. A thin coat is sufficient; you do not need to look as though you have applied a face mask.
4. Sleep on a pillowcase you do not mind getting oily.

There is no meaningful benefit to daily slugging for most people. Two or three nights a week during dry seasons is a sensible approach for those with dry or very dehydrated skin. If you wake up with skin that feels congested or appears more broken out, your skin is telling you that this is not working for it.

The trend versus the tool

Slugging went viral because it works visibly and immediately for people with dry skin in dry climates, and because before-and-after skin content performs well regardless of the subject matter. The trend is over in the sense that it is no longer novel, but the underlying practice is simply competent barrier care.

If it applies to your skin type, it is worth trying — the barrier is low and petroleum jelly is inexpensive. If your skin runs oily or acne-prone, you have probably already made the right call in sitting this one out.