What Is Slugging? Nighttime Moisture Locking
Prepared by Pharmacist Berfin Işık. As a pharmacist specializing in pharmaceutical and cosmetic formulation, she keeps up with the latest scientific literature on skin barrier and hydration. This content is for informational purposes only and does not substitute for medical advice.
Slugging is a method of locking in moisture by covering the skin with an occlusive layer as the final step of a nighttime routine; it gets its name from the shiny appearance it leaves on the skin. When applied to the right skin type, it can be effective against dryness and water loss; however, when applied to the wrong skin type, it can trigger acne. In this guide, we will explore what slugging is, who it is suitable for, and how to do it safely, from a pharmacist's perspective.
What is Slugging?
Slugging is the practice of applying a thin layer of an occlusive product (classically Vaseline/petrolatum, or a rich barrier cream) to the very top of the skin after cleansing and moisturizing, and leaving it on overnight. The goal is not to moisturize the skin, but to lock in the underlying moisture and minimize transepidermal water loss (TEWL) throughout the night.
Scientific Rationale: How Does Occlusion Work?
Occlusive agents form a physical film on the skin surface, slowing down water evaporation. In vivo studies show that petrolatum provides the most effective occlusion among the tested oils and significantly reduces TEWL. Petrolatum has also been reported to have an immediate barrier repair effect on stratum corneum with depleted lipids. Thus, while slugging may seem like a modern trend, it is underpinned by the long-known science of occlusion. We discussed how the barrier works as a whole in our skin barrier guide.
Who Is It Suitable For, and Who Is It Not?
Slugging is especially beneficial for dry, very dry, mature, and compromised skin; skin that dries out in winter or in cold-dry climates; and skin experiencing irritation from retinol/acid use. Conversely:
- It is not recommended for oily, acne-prone, and fungal acne-prone skin: Occlusion can create a warm, moist environment for sebum and microorganisms, potentially triggering acne and fungal acne.
- It should not be applied over actives: Applying an occlusive over potent actives like retinol or acids can excessively increase absorption and irritation. Actives should not be used on slugging nights.
How to Do It?
The correct order is as follows: gentle cleansing → (optional) hyaluronic acid/hydrating serum → barrier-friendly moisturizer → a thin occlusive layer on top. In the morning, gently cleanse. Slugging can be done 1-3 times a week, depending on the skin's needs, rather than every night. Instead of petrolatum, a rich night cream containing ceramides and barrier lipids also offers a lighter alternative; we discussed ceramides in our ceramide guide, and the approach to sensitive skin in our sensitive skin article.
Recommended Products
Frequently Asked Questions
Does slugging clog pores?
Petrolatum itself is not considered comedogenic; however, occlusion creates a sealed environment for underlying sebum and microorganisms. Therefore, it can trigger acne in oily and acne-prone skin. Dry and compromised skin generally benefits.
Can I slug every night?
Not necessary. 1-3 times a week is sufficient, depending on the skin's needs. It can be preferred especially during winter or on nights when skin feels dry after using retinol/acids.
Can I use retinol on slugging nights?
No. Applying an occlusive over potent actives like retinol or acids excessively increases absorption and the risk of irritation. Plan slugging for nights when you are not using actives.
Do I have to use Vaseline?
No. Petrolatum is the classic option, but rich night creams containing ceramides and barrier lipids also offer a lighter and more skin-friendly slugging experience; these formulas are particularly preferred for the face.
Conclusion
Slugging, when applied to the right skin type, is an occlusion method with strong scientific backing that reduces moisture loss. It provides a safe moisture lock for dry and compromised skin, but caution should be exercised for oily and acne-prone skin. You can get support from Medicblu experts to determine if it is suitable for your skin and to choose the right product.
References
- Patzelt A, Lademann J, Richter H, et al. In vivo investigations on the penetration of various oils and their influence on the skin barrier. Skin Res Technol. 2012;18(3):364-369. PMID: 22092829 · DOI: 10.1111/j.1600-0846.2011.00578.x
- Lodén M. Role of topical emollients and moisturizers in the treatment of dry skin barrier disorders. Am J Clin Dermatol. 2003;4(11):771-788. PMID: 14572299 · DOI: 10.2165/00128071-200304110-00005
