Skin Flooding: What Layering on Damp Skin Does, and Whether You Need It
Start with our pillar guide: What Is the Skin Barrier? The Science of Hydration, Ceramides and Occlusives, or browse all Skincare Fundamentals articles.
Skin flooding means layering water-based hydrators, usually a mist or toner and then a humectant serum, on damp skin and sealing them with a moisturizer. No study has tested skin flooding by name. Ingredient studies suggest the seal matters most: glycerin raised hydration while water loss stayed high, and petrolatum cut water loss. Evidence: Limited.
This page explains what each layer does, whether you need more than 1 moisturizer, and who can skip the routine. For where hydration fits in a full routine, see our step-by-step skincare routine order guide.
Key takeaways
- In a forearm study on irritated skin, glycerin raised skin hydration while transepidermal water loss "remained high" (Atrux-Tallau et al., 2010).
- Petrolatum reduced transepidermal water loss on the forearm in a 54-person within-person randomized trial (Rubio-Santoyo et al., 2025).
- In a 9-day human skin explant (lab) study, low-molecular-weight hyaluronic acid increased water loss by 55.5% (Sundaram et al., 2016).
- A 2003 review notes that moisturizers "often contain humectants" alongside fats (Lodén, 2003).
- No study compares skin flooding with a single moisturizer, or damp with dry application.
What is skin flooding?
Skin flooding is a multi-step hydration routine: damp skin, then a mist or toner, then a humectant serum such as hyaluronic acid or glycerin, then a moisturizer to seal it in. It is a routine, not an ingredient, and no published study tests it by name.
The logic rests on 2 kinds of ingredients. A humectant is a water-attracting ingredient that pulls water into the stratum corneum, the outermost layer of skin. An occlusive is a film-forming ingredient that slows transepidermal water loss (TEWL), meaning water evaporating out through the skin. Our guide to the skin barrier, hydration and occlusives covers both in more depth. The idea that damp skin adds a benefit has no study behind it in our sources, so treat it as convention. Evidence: no studies of the routine.
What does each skin flooding layer actually do?
The humectant layer adds water to the outer skin, and the occlusive layer keeps it from escaping. The studies suggest a humectant alone doesn't stop water loss.
Humectants hydrate but don't seal. In a forearm study, researchers irritated skin with a detergent (sodium lauryl sulphate), then applied 1% to 10% glycerin in water for 3 hours (Atrux-Tallau et al., 2010). Glycerin enhanced hydration "without restoring skin barrier function," with TEWL values that "remained high." The effect was strong at low doses and saturable, so more glycerin wasn't better past a point. The abstract doesn't report the number of participants; it lists non-US government support.
Occlusives cut water loss. In a within-person randomized trial of 54 healthy adults, petrolatum and extra virgin olive oil both raised hydration, but only petrolatum also reduced TEWL (Rubio-Santoyo et al., 2025). Duration wasn't reported in the abstract, and 1 author is employed by a pharmaceutical research company. A separate trial of 60 healthy adults found Vaseline and a foam base decreased TEWL; its authors declared no conflicts (Ordoñez-Toro et al., 2022). Both trials used the forearm.
On dry leg skin, direct petrolatum and a petrolatum-depositing body wash both improved barrier measures compared with a regular body wash (Wei et al., 2021). The authors are Procter & Gamble scientists, and n and duration weren't reported in the abstract. Evidence: Limited.
| Atrux-Tallau et al., Arch Dermatol Res, 2010 | Not reported | 3 h application; measured at 15 and 30 min | 1% to 10% glycerin in water | Hydration up; TEWL remained high |
| Rubio-Santoyo et al., J Clin Med, 2025 | 54 | Not reported | Petrolatum vs olive oil | Both raised hydration; only petrolatum cut TEWL |
| Ordoñez-Toro et al., Int J Environ Res Public Health, 2022 | 60 | Not reported | 5 bases incl. Vaseline | Foam and Vaseline decreased TEWL |
| Wei et al., Int J Cosmet Sci, 2021 | Not reported | Not reported | Petrolatum vs body washes | Petrolatum and depositing wash improved barrier measures |
Atrux-Tallau et al., Arch Dermatol Res, 2010
Result: Hydration up; TEWL remained high
Forearm skin irritated with 10% SLS first. Non-US government support. Evidence: Limited.
Rubio-Santoyo et al., J Clin Med, 2025
Result: Both raised hydration; only petrolatum cut TEWL
Within-person randomized, healthy forearm skin. 1 author employed by a pharmaceutical research company. Evidence: Limited.
Ordoñez-Toro et al., Int J Environ Res Public Health, 2022
Result: Foam and Vaseline decreased TEWL
Within-person randomized, healthy forearm skin. No conflicts declared. Evidence: Limited.
Wei et al., Int J Cosmet Sci, 2021
Result: Petrolatum and depositing wash improved barrier measures
Dry leg skin. Funding not reported in abstract. Evidence: Limited.
None of these studies tested skin flooding or facial skin.
Does the type of hyaluronic acid matter?
Possibly, but the only data are from lab skin, not people. In explants, small hyaluronic acid (HA) fragments increased water loss while larger HA reduced it.
A pilot study applied each HA daily for 9 days to living human skin explants, which are pieces of donated skin kept alive in the lab (Sundaram et al., 2016). TEWL fell 27.8% with a crosslinked HA and 15.6% with high-molecular-weight HA, but rose 55.5% with low-molecular-weight HA. The crosslinked HA is also sold as an injectable filler, and funding wasn't reported in the abstract. Product labels often don't state HA size, and no human study confirms this. If you also use a retinoid, see whether hyaluronic acid pairs with retinol. Evidence: Lab / animal only.
Is skin flooding better than one good moisturizer?
Nobody has compared the two. Because many moisturizers already combine humectants and occlusive fats, 1 well-made moisturizer may cover much of what the extra layers do.
A 2003 review notes that moisturizers "often contain humectants" and that "large differences also exist between moisturizing creams" (Lodén, 2003). Single ingredients can do both jobs too. In a 20-person forearm test, a keratin hydrolysate cream cut TEWL by 30% and raised hydration by up to 19% in men and 22% in women (Mokrejš et al., 2017). A review describes beeswax as occlusive, humectant and emollient at once (Nong et al., 2023); PubMed lists Burt's Bees, a beeswax-product brand, as a funder.
Fewer steps may also be easier to keep up. The same review says moisturizer efficacy likely depends on dosage, and that "compliance is a great challenge" (Lodén, 2003).
| Feature | Skin flooding | One moisturizer |
|---|---|---|
| Steps | 3 to 4 layers on damp skin | 1 layer |
| Humectant | Separate serum | Often built in |
| Occlusive seal | Final moisturizer | Same product |
| Head-to-head data | None | None |
| Irritation exposure | More ingredients per routine | Fewer ingredients |
Bottom line: Untested either way. The seal has the clearest evidence; extra humectant layers are optional.
Evidence: Limited (no direct comparison).
Who might benefit from skin flooding, and who can skip it?
No study addresses who benefits. As expert opinion, skin flooding may suit skin that feels dry or tight, while people with oily skin, comfortable skin or a dislike of heavy layers can likely skip it.
Each added product carries its own risk. The 2003 review warns that "some formulations may deteriorate the skin condition," that emulsifiers "may weaken the barrier," and that low pH and sensory reactions from ingredients like lactic acid and urea may reduce acceptance (Lodén, 2003). It also notes that greasy textures and strong odors may be disagreeable. If you use a prescription treatment, ask your clinician before adding layers; don't change the treatment itself. Evidence: Expert opinion.
What if your barrier is already damaged?
If your skin is stinging, flaking or reacting, barrier repair comes before extra hydration steps. Our guide to fixing a damaged skin barrier covers that in detail.
The occlusive step has the most relevant data here. Petrolatum "has an immediate barrier-repairing effect in delipidized stratum corneum" (Lodén, 2003), and a 2016 review lists petrolatum among conventional therapies for atopic dermatitis (Nomura and Kabashima, 2016). In a lab model, petrolatum served as the reference "efficient impermeable barrier against hydrophilic molecules" (Casiraghi et al., 2017). If you want a serum layer that does more than hydrate, see our peptide ingredients ranking. Evidence: Limited.
Where the evidence stops
- No study tests skin flooding or compares a multi-layer routine with a single moisturizer.
- No damp vs dry data. Applying to damp skin is untested convention.
- No facial data. Human studies used forearm or leg skin, were small, and mostly didn't report duration.
- HA size data are explant-only.
- No data on breakouts or pilling from layering.
- Pregnancy, breastfeeding and drug interactions aren't covered; ask a clinician.
FAQ
What is skin flooding?
Skin flooding means layering water-based hydrators, usually a mist or toner and then a humectant serum, on damp skin and sealing them with a moisturizer. No study has tested the routine by name, so its claimed benefits come from studies of individual ingredients.
Does hyaluronic acid or glycerin alone hydrate skin?
Humectants such as glycerin draw water into the outer skin layer. In a forearm study on irritated skin, glycerin raised hydration, but water loss through the skin remained high, which is why a sealing layer is thought to matter.
Do I need the occlusive step in skin flooding?
The ingredient evidence points that way. Petrolatum reduced transepidermal water loss in a 54-person within-person randomized trial, and Vaseline decreased it in a 60-person trial, both on healthy forearm skin.
Is skin flooding better than one good moisturizer?
Nobody has compared them. Moisturizers often already contain humectants alongside fats, so a single well-made moisturizer may do much the same job, but that is expert opinion, not a tested result.
Can the wrong hyaluronic acid make skin flooding worse?
In a 9-day lab study on human skin explants, low-molecular-weight hyaluronic acid increased water loss by 55.5%, while high-molecular-weight hyaluronic acid reduced it by 15.6%. This has not been confirmed in people.
Does applying products to damp skin make a difference?
We found no study comparing damp and dry skin application. Applying to damp skin is a common recommendation, but in our sources it is untested convention.
Who can skip skin flooding?
No study addresses this. As expert opinion, people whose skin already feels comfortable, or who have oily skin or dislike heavy layers, may not need the extra steps.
Can skin flooding irritate skin?
No study has measured irritation from skin flooding itself. A review notes that some moisturizer formulations may worsen skin condition and that ingredients such as lactic acid and urea can cause sensory reactions, so every extra layer is another chance for one.
References
- Lodén M. Role of topical emollients and moisturizers in the treatment of dry skin barrier disorders. Am J Clin Dermatol. 2003. Review; non-US government support. https://pubmed.ncbi.nlm.nih.gov/14572299/
- Atrux-Tallau N, et al. Effects of glycerol on human skin damaged by acute sodium lauryl sulphate treatment. Arch Dermatol Res. 2010. Human forearm study, n not reported, 3 h application; non-US government support. https://pubmed.ncbi.nlm.nih.gov/20043170/
- Sundaram H, et al. Pilot Comparative Study of the Topical Action of a Novel, Crosslinked Resilient Hyaluronic Acid on Skin Hydration and Barrier Function in a Dynamic, Three-Dimensional Human Explant Model. J Drugs Dermatol. 2016. Pilot human skin explant study, 9 days; funding not reported in abstract. https://pubmed.ncbi.nlm.nih.gov/27050698/
- Rubio-Santoyo A, et al. Effects of Extra Virgin Olive Oil and Petrolatum on Skin Barrier Function and Microtopography. J Clin Med. 2025. Within-person randomized trial, n=54, duration not reported; 1 author employed by a pharmaceutical research company. https://pubmed.ncbi.nlm.nih.gov/40649050/
- Ordoñez-Toro A, et al. The Assessment of Skin Homeostasis Changes after Using Different Types of Excipients in Healthy Individuals. Int J Environ Res Public Health. 2022. Within-person randomized trial, n=60; no conflicts declared. https://pubmed.ncbi.nlm.nih.gov/36554558/
- Wei K, et al. Effects of petrolatum, a petrolatum depositing body wash and a regular body wash on biomarkers and biophysical properties of the stratum corneum. Int J Cosmet Sci. 2021. Leg-wash protocol on dry skin, n and duration not reported; funding not reported in abstract. Author affiliation: Procter & Gamble. https://pubmed.ncbi.nlm.nih.gov/33336384/
- Mokrejš P, et al. Preparation of Keratin Hydrolysate from Chicken Feathers and Its Application in Cosmetics. J Vis Exp. 2017. Forearm test, n=20, up to 48 h; funding not reported in abstract. https://pubmed.ncbi.nlm.nih.gov/29286371/
- Nong Y, et al. A review of the use of beeswax in skincare. J Cosmet Dermatol. 2023. Narrative review of 5 studies (3 animal, 2 human). PubMed lists Burt's Bees as a funder. https://pubmed.ncbi.nlm.nih.gov/36999457/
- Nomura T, Kabashima K. Advances in atopic dermatitis in 2015. J Allergy Clin Immunol. 2016. Review. https://pubmed.ncbi.nlm.nih.gov/27931536/
- Casiraghi A, et al. In vitro method to evaluate the barrier properties of medical devices for cutaneous use. Regul Toxicol Pharmacol. 2017. In vitro validation study. https://pubmed.ncbi.nlm.nih.gov/28822878/
Disclosure: This article is for general information only. It is not medical advice. Peptide Skincare has no affiliate links in this article and received no payment from any manufacturer mentioned. Talk to a dermatologist if your skin stays dry, itchy or irritated despite moisturizing.