Slugging: The Science Behind the Trend — Does It Work and Who Should Do It?
Slugging — applying a thin layer of petrolatum (Vaseline or similar) as the absolute final PM step over a completed skincare routine — went from a Korean beauty practice to a global skincare trend in the early 2020s. The name comes from the shiny, moist appearance it gives skin overnight. The principle has genuine dermatological backing: petrolatum is the most effective occlusive agent in skincare, with decades of clinical use in wound healing, eczema management, and barrier repair. The trend popularised something dermatologists had been quietly recommending for years for dry and compromised skin. That said, it is not appropriate for all skin types, and the "put Vaseline over everything" advice that circulates online misses some important nuance about how it interacts with a routine.
Quick Answer
Slugging works by creating a near-impermeable occlusive barrier that dramatically reduces overnight transepidermal water loss — skin retains significantly more moisture through the night, waking plump and soft. The mechanism is well-established. It is most beneficial for dry, very dry, dehydrated, compromised-barrier, eczema-adjacent, and mature skin. It is not appropriate for oily or acne-prone skin — petrolatum does not cause acne directly, but its extreme occlusion traps heat and sebum in a way that can worsen congestion. Apply over a fully absorbed routine, not instead of it. Use a pea-sized amount — a thick layer is unnecessary and counterproductive.
The Science: What Petrolatum Actually Does
Petrolatum (petroleum jelly) is a semi-solid mixture of hydrocarbons. It is the most effective occlusive agent in cosmetic and dermatological use — studies measuring transepidermal water loss (TEWL) consistently find petrolatum reduces TEWL by 98% compared to untreated skin, significantly outperforming all other occlusive ingredients including dimethicone, mineral oil, lanolin, and beeswax. It achieves this by forming a continuous hydrocarbon film across the stratum corneum surface that water molecules cannot easily cross.
It does not penetrate the skin — it sits on the surface. This means it is not delivering active ingredients to the skin; it is preventing water from escaping from the skin. The distinction matters for understanding when slugging helps: if the skin beneath the petrolatum layer is well-hydrated (because you applied humectants and a ceramide moisturiser first), slugging locks that hydration in overnight. If you apply petrolatum to dehydrated skin without a humectant layer beneath, you are trapping what little water is there without adding more — still somewhat beneficial, but less effective.
Does Petrolatum Cause Acne? Clearing Up the Myth
Petrolatum has a comedogenicity rating of 0 — it does not block pores in the conventional sense. The research that established comedogenicity ratings consistently found petrolatum non-comedogenic in human skin models. This is why it is used in wound healing and post-procedure care for all skin types without triggering breakouts.
However, this does not mean it is safe for all acne-prone skin in the slugging context. Slugging creates a warm, occlusive microenvironment overnight. For oily skin with active acne, this environment can exacerbate congestion not through comedogenicity but through heat and sebum accumulation — the occlusion traps the skin's own sebum more effectively than it would be trapped under normal conditions. The practical guidance is: petrolatum is non-comedogenic as a wound-healing agent applied to small areas; as a whole-face overnight occlusive on oily or acne-prone skin, the occlusion effect itself may worsen acne regardless of the ingredient's formal comedogenicity rating.
Who Should Slug and Who Should Not
| Skin Profile | Slugging? | Why |
|---|---|---|
| Very dry / dry skin | Yes — highly beneficial | Maximum TEWL reduction dramatically improves overnight moisture retention; addresses the core problem |
| Dehydrated (any skin type) | Yes — with humectant layer beneath | Locks in humectant-delivered moisture; addresses winter and low-humidity TEWL |
| Compromised barrier / eczema-adjacent | Yes — standard recommendation | Petrolatum is clinically used for eczema barrier management; reduces flare triggers from environmental stressors |
| Mature skin | Yes — particularly in winter | Ageing barrier produces less natural occlusion; overnight slugging compensates meaningfully |
| Normal skin | Optional — situational benefit | Beneficial in dry/cold conditions; less necessary in humid environments |
| Oily skin | Not recommended | Risk of exacerbating congestion through heat/sebum trapping despite low comedogenicity rating |
| Active acne (inflammatory) | Not recommended | Same occlusion concern; avoid until acne is controlled |
| After retinoid application | Caution — use minimal amount | Occlusion increases retinoid penetration beyond intended level; can intensify irritation |
How to Slug Correctly
The technique matters. The correct protocol: complete your full PM routine (cleanser → serums → moisturiser), wait for everything to fully absorb (10–15 minutes), then apply a pea-sized amount of petrolatum spread thinly across the face. A thick layer does not improve efficacy — a thin, even film achieves the same TEWL reduction and is significantly less uncomfortable to sleep in. Vaseline Original is the most accessible product; La Roche-Posay Cicaplast Baume and CeraVe Healing Ointment combine petrolatum with additional barrier-repairing ingredients for a more functional formulation. Do not slug over an unadsorbed retinoid — let the retinoid fully absorb first or use the sandwich technique separately. On retinoid nights, skip slugging or apply a very minimal amount and accept that penetration may be slightly enhanced.
For a complete overview of occlusive ingredients and how they fit into a PM layering sequence, see our guides on how to layer facial oils and skincare layering order science. Build your PM routine in the Skin Stacker Routine Builder to confirm petrolatum is correctly positioned as the final step.