Slugging — Is Overnight Petroleum Jelly a Genius Trick or a Trap?

What is slugging?

Slugging (from the word "slug") is the final step of an evening skincare routine that involves applying a thin layer of petroleum jelly to the face. The result? Your skin looks as if it's coated in snail slime — hence the name. The trend exploded on TikTok and Reddit, but the method itself isn't new. Dermatologists have recommended petroleum jelly as an occlusive for decades to treat extremely dry skin, eczema, or to support recovery after dermatological procedures.

The question is: is it a method for everyone, or a trend that could do more harm than good?

How petroleum jelly works — the science behind occlusion

Petrolatum (white petroleum jelly) is one of the most effective occlusive ingredients in dermatology. Studies show that it reduces transepidermal water loss (TEWL) by up to 98%. By comparison: plant oils reduce TEWL by 20–30%, and silicones by roughly 20–30%.

Petroleum jelly doesn't hydrate the skin on its own — it creates a physical barrier that locks water inside. That's why it's essential to apply it onto already-hydrated skin (after toner, serum and moisturiser). Without a hydrating layer underneath, slugging is pointless — you'd just be sealing in nothing.

Worth knowing: modern cosmetic-grade petroleum jelly is highly purified and contains none of the carcinogenic substances that can be present in crude petroleum. Concerns about "petrolatum = crude oil on your face" stem from a misunderstanding of the refining process. You'll find more about occlusive ingredients in our ingredient encyclopedia.

When does slugging help?

Petroleum-jelly occlusion has proven benefits in specific situations:

• Very dry skin — when standard moisturisers aren't enough, especially in winter when humidity is low
• A damaged skin barrier — after overdoing acids or retinoids, or following dermatological treatments (peels, lasers)
• Eczema and atopic dermatitis — petroleum jelly is recommended by the AAD (American Academy of Dermatology) as a safe occlusive
• Chapped lips and the area around the nose — the classic use case: effective and inexpensive

In these cases, slugging isn't a trend — it's a proven dermatological method.

When does slugging do harm?

And this is where the problem begins with promoting the method uncritically as a one-size-fits-all solution:

• Acne-prone and oily skin — petroleum jelly is comedogenic at a rating of 0–1 (low), but sealing in sebum, bacteria and makeup residue underneath it can worsen blackheads and inflammation. People with active acne should avoid slugging the entire face.
• Skin prone to fungal acne (Malassezia) — occlusion creates a warm, moist environment that encourages yeast to multiply
• After applying high-concentration active ingredients — retinol and AHA/BHA acids penetrate more deeply under petroleum jelly, which can lead to irritation. If you use actives, don't apply petroleum jelly directly on top of them.

How to slug safely

1. Cleanse your face thoroughly — double cleansing makes sense here, so you don't seal impurities under the occlusive.
2. Apply hydration — a hydrating toner, a hyaluronic acid serum, a moisturising cream. Petroleum jelly is the "seal", not the "filler".
3. Skip the actives — slugging nights are nights without retinol or acids.
4. Use a thin layer — a pea-sized amount is enough for the whole face. A thick layer doesn't work better, it just stains your bedding.
5. Don't do it every day — 2–3 times a week is enough, unless your skin is extremely dry.

Alternatives to petroleum jelly

If the texture of petroleum jelly isn't for you, other occlusive ingredients (though less effective) include: shea butter, squalane, jojoba oil and lanolin (note: a strong contact allergen for some people). There are also so-called "sleeping masks" — overnight masks with a lighter consistency that serve a similar function. Read how to read a cosmetic's ingredient list to judge whether your overnight mask contains effective occlusives.

Summary

Slugging is neither a revolution nor a scam. It's an old dermatological method that works in specific situations — dry skin, a damaged barrier, post-treatment recovery. For people with acne or oily skin it can be a problem. Like any trend, it calls for a critical approach: not every skin type needs petroleum jelly, but the skin that does will genuinely benefit from it.

Check the occlusivity of the ingredients in your cream →