Is Slugging Actually Good for Your Skin? What 98% TEWL Reduction Really Means
🐌 Summary: TL;DR — Slugging works by blocking up to 98% of transepidermal water loss. It's excellent for dry and barrier-compromised skin, but can aggravate oily or blemish-prone skin by trapping oil and bacteria.
What does slugging actually do to your skin?
Slugging is the practice of applying a thick occlusive — usually petroleum jelly (Vaseline) — as the last step of your nighttime routine. The name comes from the slug-trail sheen it leaves on your face.
The science behind it is straightforward. Your skin constantly loses water through evaporation — a process called transepidermal water loss (TEWL). Research has shown that petroleum jelly reduces TEWL by up to 98% — more than any other moisturizing ingredient. By comparison, mineral oil blocks about 40%, and typical moisturizers block 20–30%.
98%
TEWL reduction from petroleum jelly — the highest of any single ingredient
Non-comedogenic
Refined petroleum jelly does not clog pores — the old study was debunked
Does Vaseline clog pores? The myth vs. the science
The myth is outdated
The belief that petroleum jelly clogs pores comes from old, poorly controlled studies. Modern dermatological research confirms that highly refined petroleum jelly is non-comedogenic. It sits on top of the skin as a barrier — it doesn't penetrate into pores. The issue isn't the Vaseline itself. It's what you seal underneath it: if you slug over dirty skin, excess oil, or pore-clogging products, those get trapped too.
Who should slug — and who should skip it?
✅ Great for
Dry skin · Dehydrated skin · Barrier-compromised skin (from over-exfoliating, retinol, or weather) · Mature skin · Dry winter climates · Night-only use
❌ Skip if
Oily or blemish-prone skin · You haven't cleansed properly · You're using actives like retinol underneath (can intensify irritation by trapping it) · Humid summer weather (skin doesn't need the occlusion)
The golden rule: Slug over clean, hydrated skin. Cleanse → hydrating toner → moisturizer → thin layer of occlusive. Never slug over actives, dirty skin, or heavy makeup residue.
This article is for informational purposes only. Not intended as medical or professional advice.
