What Is the Skin Barrier? The Science of Hydration, Ceramides and Occlusives

Direct answer: What is the skin barrier? It is the stratum corneum, the skin's outermost dead-cell layer, which holds water in and keeps irritants out. Human trials support regular moisturizer use, with glycerol, petrolatum and complete ceramide-cholesterol-fatty acid mixes each helping. A Cochrane review found no reliable evidence that one moisturizer beats another. Evidence: moderate.

Skin feels damaged right now? Go to our step-by-step guide to skin barrier repair: how to fix a damaged skin barrier. This page explains the science behind it.

Key takeaways

• Nobody agrees on a "normal" TEWL number. Transepidermal water loss in healthy adults runs from 2.3 g/m²/h on the breast to 44.0 g/m²/h in the armpit (Akdeniz et al., 2018). Any chart that labels your skin "healthy" or "damaged" from one cutoff number is made up.
• Moisturizers work, but no brand is clearly better. A Cochrane review of 77 RCTs (6,603 people with eczema) found fewer flares with moisturizers. It found no reliable evidence that one moisturizer outperforms another (van Zuuren et al., 2017). Evidence: well-established (in eczema).
• Petrolatum does more than sit on top. In human volunteers, it sped up barrier recovery by moving into the gaps between stratum corneum cells (Ghadially et al., 1992). Evidence: limited.
• Lipid ratios matter less than lipid completeness. Partial lipid mixes delayed repair. Equimolar mixes allowed normal repair. Raising any one lipid up to 3-fold sped it up (Man et al., 1996). Evidence: mostly animal data.
• Peptides are a weak fit for barrier repair. The only peptide barrier result in our source set is a 24-person study of acetyl hexapeptide-3 (Raikou et al., 2017). Evidence: early / preliminary.

This guide is the foundation of our Skincare Fundamentals pillar. If you also use actives like peptides or retinoids, read it alongside our step-by-step skincare protocol. A barrier that can't hold water makes every other step harder to tolerate.

What is the skin barrier?

Most articles describe the barrier as "bricks and mortar." Corneocytes (flattened dead skin cells) are the bricks. A lipid matrix of ceramides, cholesterol and free fatty acids is the mortar. That picture is accurate but incomplete.

A 2023 review in Skin Pharmacology and Physiology describes the barrier as 4 overlapping functional layers (Rajkumar et al., 2023):

1. Physical: corneocytes and the lipid matrix that slows water loss and blocks irritants.
2. Chemical: the skin's acidic surface pH and the enzymes that depend on it, including those involved in making ceramides.
3. Microbiologic: the commensal (resident, normally harmless) microbes living on the skin surface.
4. Immunologic: immune signaling that responds when the barrier is breached.

This matters for repair because a product can act on more than 1 layer. The same review notes that acidic moisturizers may support barrier enzymes, ceramide production and commensal bacteria, in addition to adding moisture (Rajkumar et al., 2023). That is a review-level argument, not a trial result, but it explains why pH comes up in barrier discussions.

The review also sorts moisturizer ingredients into 3 jobs (Rajkumar et al., 2023):

• Occlusives form a seal over the stratum corneum surface to slow evaporation.
• Humectants draw water from the dermis into the epidermis.
• Emollients blend into the stratum corneum and smooth it.

Most barrier creams combine all 3. Keep these categories in mind, because the evidence differs for each.

What is TEWL, and is there a healthy cutoff?

Transepidermal water loss (TEWL) is the rate at which water evaporates through the skin, measured in grams per square meter per hour (g/m²/h). Researchers use it as the main objective sign of barrier function. Higher TEWL means more water is escaping.

You may have seen charts saying healthy skin sits at 5–10 g/m²/h and damaged skin goes above 25. We couldn't find a primary source for those thresholds, and the reference data don't support them.

The largest analysis we found pooled 212 studies covering 86 skin areas in healthy adults (Akdeniz et al., 2018):

Source: Akdeniz et al., 2018, meta-analysis update of 212 studies in healthy adults.

The original version of this analysis (167 studies, 50 skin areas) found that TEWL in adults 65 and older was consistently lower than in adults 18–64. The authors also said there is no agreed definition of "normal" TEWL (Kottner et al., 2013).

Here's what that means in practice:

• A single TEWL reading from a skin-analysis gadget means little without a matched site and a baseline.
• Older skin often feels drier, but by this measure it isn't simply "leakier." Lower water loss and dryness are different things.
• Studies compare TEWL before and after, or treated site against untreated site, on the same person. That is how you should read any TEWL claim too.

Evidence: well-established (for site-dependence and the lack of a universal normal value).

Does drinking water hydrate your skin?

Our old version of this article said drinking water "does remarkably little" for skin. That was too strong. The evidence is thin in both directions.

In the most direct study we found, 34 healthy women (mean age 24.5) added 2 liters of water a day for 30 days. Superficial and deep skin hydration both rose, most clearly in people who usually drank less. TEWL did not change significantly (Palma et al., 2015). The abstract describes no control group, so you can't separate the water from season, measurement drift or expectation.

A fair reading:

• Extra water may modestly raise skin water content, especially if you drink little to begin with.
• It showed no effect on barrier function as measured by TEWL.
• One small study without a control group can't settle the question.

Evidence: early / preliminary. Staying hydrated is reasonable for many reasons. Just don't expect it to fix a barrier you irritated with over-exfoliation.

Which humectant has the best evidence for the skin barrier?

Humectants pull water into the stratum corneum. Common examples are glycerol (glycerin), urea, hyaluronic acid and sodium PCA. Glycerol is the best studied of these for barrier recovery.

In 2 in vivo studies, researchers disrupted skin either by tape stripping (3-day follow-up) or by washing with sodium lauryl sulfate, a harsh detergent (7-day follow-up). Glycerol-treated sites repaired faster by TEWL and had higher stratum corneum hydration. The benefit lasted 7 days after treatment stopped (Fluhr et al., 1999). Sample size was not reported in the abstract. Evidence: limited.

The Cochrane review adds clinical outcomes in eczema (van Zuuren et al., 2017):

• With a glycerol moisturizer, more participants noticed improvement than with control (RR 1.22, meaning about 22% more people reported improvement).
• Urea cream improved dryness (RR 1.40) but caused more adverse events (RR 1.65), mostly stinging and irritation-type reactions.

Now the limit. A 2025 trial included a glycerine-only oil-in-water cream as its comparator. That cream reduced dryness but had no effect on barrier function. TEWL after tape stripping went from 35.6 to 37.4 g/m²/h, which is no improvement (Andrew et al., 2025).

So glycerol can make skin feel and look less dry, and in acute-damage models it sped TEWL recovery. In this more recent trial, though, a glycerine-only cream didn't strengthen the barrier on its own. That fits the idea that humectants mainly add water while lipids rebuild the structure that holds it in. Evidence for glycerol overall: moderate.

Do occlusives and slugging help the skin barrier?

"Slugging" means putting a layer of petrolatum (petroleum jelly) on top of your routine overnight. A recurring debate in skincare communities is whether it actually repairs anything or just traps water under a film and hides the problem.

The best evidence we have is older but direct. In human volunteers whose barrier was disrupted with acetone, petrolatum accelerated barrier recovery. Microscopy showed it moving into the spaces between stratum corneum cells and replacing intercellular lipid layers, not just sitting on the surface (Ghadially et al., 1992). Sample size and duration were not reported in the abstract. Evidence: limited.

So the "it just masks" argument is only half right. Petrolatum does seal the surface. That same study also suggests it takes part in repair at the lipid level.

What we don't know:

• Whether nightly slugging helps intact or acne-prone skin beyond what a regular moisturizer does. We found no trial of that in our source set.
• How it compares head-to-head with ceramide creams. The Cochrane review's broader finding, no reliable evidence that one moisturizer beats another, suggests the differences may be small (van Zuuren et al., 2017).

If you try slugging, use a thin layer as the last step at night. If you're breakout-prone, watch how your skin responds over a few weeks before deciding.

Does the ceramide, cholesterol and fatty acid ratio matter?

The "3:1:1 ceramide-dominant ratio" is one of the most repeated barrier claims online. It comes from a real research program at UCSF, but the findings are more nuanced than the slogan.

The core finding: completeness matters most

In barrier-disrupted skin, mostly in mice with similar preliminary results in damaged human skin, researchers found that ceramides, cholesterol and free fatty acids are all required (Man et al., 1996):

• Applying only 1 or 2 of the 3 lipids delayed barrier recovery.
• An equimolar mix (equal molecular amounts of all 3) allowed normal recovery.
• Raising any one of the 3, up to 3-fold, sped up repair.

Notice the last point. The acceleration came from making any lipid dominant, not only ceramides. Evidence: lab / animal, with preliminary human data.

Aged skin responded to a different ratio

A follow-up looked at aged mice and aged human skin (participants around 80 ± 5 years). After tape stripping, a cholesterol-dominant 3:1:1:1 mixture sped barrier recovery at 6 hours in aged human skin (n=6, p<0.005). A fatty-acid-dominant mixture delayed recovery in aged mice (Zettersten et al., 1997). Evidence: early / preliminary.

What this means for product labels

• "Ceramide-dominant 3:1:1 is the ratio" oversimplifies the work. The original data support a complete mix, with any one lipid raised.
• In the small aged-skin study, cholesterol dominance worked best.
• Incomplete formulas, for example a single ceramide with no cholesterol or fatty acids, are what this research flags as potentially counterproductive.
• Most brands don't disclose their molar ratios. A ratio printed on a label is marketing until the company shows its formulation data.

Do ceramide creams support the skin barrier in human trials?

Two recent controlled trials tested lipid-based barrier creams on TEWL and skin condition.

Andrew et al., 2025: a double-blind, intra-participant trial (one limb treated with each product) in 58 adults with a history of eczema, lasting 28 days. A physiological-lipid multivesicular emulsion with glycerine lowered TEWL after 20 tape strips from 38.02 to 29.79 g/m²/h (P<0.001). The glycerine-only comparator showed no change. Ceramide NP(18) rose 24% and ceramide AP(18) rose 19% on the lipid side. Funding was not reported in the abstract. Evidence: limited.

Spada et al., 2021: an RCT in adults with moderate eczema, lasting 28 days, comparing a ceramide-dominant cream plus cleanser against placebo. TEWL (P=.034) and hydration (P<.0001) improved more with the active products. EASI, the clinical eczema severity score, improved in both groups with no difference between them (P=.78). Sample size was not reported in the abstract. The study was sponsored by Ego Pharmaceuticals, the manufacturer, and most authors were employees. Evidence: limited.

Taken together:

• Lipid creams improved measurable barrier markers (TEWL, hydration, stratum corneum ceramides) over 28 days.
• In the trial that measured clinical severity, placebo did just as well. Placebo creams are moisturizers too, which fits the Cochrane conclusion.
• Both trials enrolled people with eczema or an eczema history. Results may not carry over neatly to barrier irritation from too many actives.

The Cochrane review remains the anchor: moisturizers lowered investigator-assessed eczema severity (12 studies, 1,281 participants) and reduced flares (6 studies, 607 participants, RR 0.33), but the authors "did not find reliable evidence that one moisturiser is better than another" (van Zuuren et al., 2017).

Does niacinamide strengthen the skin barrier?

Niacinamide (nicotinamide, a form of vitamin B3) isn't a peptide, but it has the most direct mechanistic link to barrier lipids of any active in our sources.

In cultured human keratinocytes, nicotinamide at 1–30 µmol/L for 6 days raised (Tanno et al., 2000):

It also upregulated serine palmitoyltransferase (SPT), a key enzyme in ceramide synthesis. In the same paper, topical nicotinamide raised stratum corneum ceramides and free fatty acids and lowered TEWL in dry skin (Tanno et al., 2000). The abstract doesn't report the topical study's sample size, duration or concentration.

Evidence: lab data plus early human data. The cell results are strong. The human part is small and thinly described. Unlike most actives, though, niacinamide works directly on the lipids a barrier needs.

Do peptides help the skin barrier?

You will often read that "ceramide-boosting peptides" make the barrier repair itself from within. We found no indexed human study that supports that. Here's what the evidence actually shows.

Acetyl hexapeptide-3 (an older INCI name for the Argireline peptide, now usually listed as acetyl hexapeptide-8): in 24 volunteers over 60 days, it lowered TEWL (Raikou et al., 2017). Design details and funding beyond this are not reported in our source notes. It is one small study. Evidence: early / preliminary.

GHK-Cu (copper tripeptide-1): it's very hydrophilic (water-loving), with a log D of about −2.4 (Badenhorst et al., 2016). That makes it hard to get through the lipid-rich stratum corneum. A 2025 review noted a "surprising absence of clinical studies" for topical GHK-Cu (Mortazavi et al., 2025). We found no human barrier trial for it. For the full picture, see our guide to what copper peptides can and can't do for skin. Evidence: no human barrier data.

Palmitoyl tripeptide-8: our old version called it "one of the most studied barrier-supporting peptides." We found no indexed human barrier study. We're making no claim about it.

The bigger problem is penetration. A 2022 review concluded that most cosmetic peptides are large, hydrophilic and ionizable. They are also exposed to skin enzymes that break them down. As a result, most "might not reach their targets in the skin at right concentrations" without delivery enhancement (Mortazavi & Moghimi, 2022).

Bottom line: peptides may have a place in your routine for other goals. Our breakdown of peptide ingredients covers what each class is meant to do. For barrier repair specifically, lipids, glycerol, petrolatum and niacinamide have more evidence than any peptide.

What does a barrier-friendly routine look like?

The barrier-support steps below are built from the studies above. Where a step is common-sense practice that no study in our sources tested, we say so.

1. Pause the likely irritant. If your barrier problems started after adding acids, retinoids, scrubs or a new strong active, stop it for now. Evidence: not directly tested in our sources; practical reasoning. None of the trials above tested continued use of irritants during repair.

2. Cleanse gently and less often. Harsh detergents are a standard way researchers damage the barrier on purpose. Fluhr's team used sodium lauryl sulfate washing as its damage model (Fluhr et al., 1999). A mild, low-foam cleanser is the logical choice. Evidence: indirect.

3. Use a moisturizer with complete lipids plus a humectant, twice daily. Look for ceramides together with cholesterol and fatty acids, rather than a single ceramide alone (Man et al., 1996). A glycerine-containing lipid emulsion improved TEWL in 28 days, while glycerine alone did not (Andrew et al., 2025). Evidence: limited. Remember that any decent moisturizer may perform similarly (van Zuuren et al., 2017).

4. Add a thin occlusive layer at night if you need it. Petrolatum sped barrier recovery in human volunteers (Ghadially et al., 1992). Evidence: limited. Skip it or use it sparingly if it seems to cause breakouts for you.

5. Consider niacinamide once your skin tolerates products again. It raised ceramides in cells and lowered TEWL in dry skin (Tanno et al., 2000). Evidence: early / preliminary in humans. Add it as a single new product, not alongside several others.

6. Be cautious with urea if you're stinging. In the Cochrane data, urea improved dryness but caused more adverse events than control (van Zuuren et al., 2017). Evidence: well-established (in eczema).

7. Give one routine a fair trial before switching. The controlled cream trials measured results at 28 days (Andrew et al., 2025; Spada et al., 2021). The water study ran 30 days (Palma et al., 2015), and the peptide study ran 60 days (Raikou et al., 2017). Recovery from acute lab damage was measured over 3–7 days (Fluhr et al., 1999). Real-world recovery time varies with how damaged your skin is, what damaged it and your skin type. We can't give you a reliable timeline.

Once your skin is comfortable again, reintroduce actives one at a time. Our skincare protocol lays out how to sequence them.

If your skin doesn't improve, is cracked or weeping, or looks like eczema or dermatitis, see a dermatologist. Persistent barrier problems sometimes need prescription treatment.

What readers keep running into

We reviewed recurring discussions in skincare communities. 3 patterns came up repeatedly. We paraphrase them here and answer each with the evidence.

"My barrier won't heal after I overdid actives." Many people describe weeks of stinging and tightness after stacking exfoliating acids and retinoids. They often keep "fixing" the problem by adding more products. The studies above used one product per site and stopped other damage. Your routine probably needs fewer products, not more.

"Is slugging repair or just a cover-up?" The 1992 petrolatum study is the clearest answer we have. It sped recovery and moved into the stratum corneum's lipid spaces (Ghadially et al., 1992). It does cover the skin, but it also appears to take part in repair.

"I switch moisturizers every week or two because nothing works." This is common, and it works against you. The trials that showed TEWL improvement measured at 28 days. If you change products every 7–14 days, you never reach the point where those studies saw results. You also can't tell which product helped or hurt.

Does GLP-1 medication affect the skin barrier?

Some people taking GLP-1 receptor agonists such as semaglutide notice skin changes and wonder whether their barrier is involved. The evidence is thin.

• A 2024 narrative review argued that GLP-1-related facial changes are multifactorial, involving loss of dermal and subcutaneous fat and changes in adipose-derived stem cells. The authors propose these may "compromise the structural integrity and barrier function of the skin" (Ridha et al., 2024). That is a hypothesis, not trial data.
• A 2026 systematic review (new, no citations yet) of 40 human studies, including case reports and observational studies, reported facial volume loss, dermal thinning and decreased elasticity. Listed risk factors included advanced age, rapid weight loss, poor hydration and insufficient protein intake (Barone et al., 2026).
• No study we found tests barrier creams or any specific skincare routine in GLP-1 users.

The general barrier evidence above applies to everyone. Questions about your medication, diet or protein intake belong with your prescribing clinician. We don't advise starting, stopping or changing any medication.

Where the evidence stops

• No universal TEWL "normal." Reference data vary hugely by body site, so home TEWL readings are hard to interpret (Kottner et al., 2013).
• Most controlled moisturizer data come from eczema. We don't know how well those results apply to barrier damage caused by cosmetic actives.
• Lipid ratio research is mostly murine, with the aged-human arm limited to 6 people (Zettersten et al., 1997).
• Key details are often missing. Sample sizes and funding are unreported in several abstracts, including Ghadially 1992, Fluhr 1999 and Spada 2021's n.
• Peptides lack barrier trials. There is one small acetyl hexapeptide-3 study and nothing indexed for GHK-Cu or palmitoyl tripeptide-8.
• Recovery timelines are unknown for everyday barrier damage. Trials measured fixed time points (3–7 days in acute models, 28–60 days in product trials) rather than "time to full recovery."
• Nothing tests barrier products in GLP-1 users.

FAQ

How long does skin barrier repair take? It varies, and real-world timelines aren't well measured; lab models show recovery over days. See how to fix a damaged skin barrier for what the recovery studies measured.

Does slugging with petrolatum repair the barrier or just cover it up? Both, according to the best data we have. In human volunteers, petrolatum sped barrier recovery and moved into the spaces between stratum corneum cells instead of only forming a surface film (Ghadially et al., 1992). Sample size wasn't reported, so treat this as limited evidence.

Is a 3:1:1 ceramide ratio necessary? Not as a fixed rule. The underlying research found that all 3 lipids are needed. Equimolar mixes allowed normal recovery, and raising any one lipid up to 3-fold sped repair (Man et al., 1996). In aged human skin, a cholesterol-dominant mix worked best (Zettersten et al., 1997).

Will drinking more water fix dry skin? Probably not on its own. In 34 women who added 2 L/day for 30 days, skin hydration rose modestly, mainly in low drinkers, but TEWL didn't change. The study had no control group (Palma et al., 2015).

Do peptide serums repair the skin barrier? There's very little evidence. One 24-person, 60-day study found acetyl hexapeptide-3 lowered TEWL (Raikou et al., 2017). Topical GHK-Cu lacks published clinical studies (Mortazavi et al., 2025). Niacinamide and lipid creams have stronger barrier data.

Why does my barrier still feel damaged after weeks of babying it? Common reasons include continued exposure to an irritant, switching products too often to see an effect, or an underlying condition like eczema or dermatitis. The controlled trials measured results at a minimum of 28 days with one product (Spada et al., 2021). Persistent symptoms are worth a dermatologist visit.

Can collagen supplements repair the skin barrier? The data are mixed, and none target barrier repair directly. A 2023 meta-analysis of 26 RCTs found improved hydration and elasticity (Pu et al., 2023). A 2025 meta-analysis of 23 RCTs found that studies not funded by industry showed no effect on hydration (Myung & Park, 2025). Evidence: mixed / contested. See our collagen supplements evidence review.

Go deeper

• Copper peptides for skin: what GHK-Cu can and can't do
• Peptide ingredients explained, class by class
• Collagen supplements: what the independent trials show
• A step-by-step skincare protocol for layering actives

References

1. Rajkumar J, et al. Review of the skin barrier's physical, chemical, microbiologic and immunologic layers and moisturizer mechanisms. Skin Pharmacol Physiol. 2023. Narrative review. https://pubmed.ncbi.nlm.nih.gov/37717558/
2. Akdeniz M, et al. TEWL in healthy adults, meta-analysis update. Br J Dermatol. 2018. Meta-analysis, 212 studies, 86 skin areas. https://pubmed.ncbi.nlm.nih.gov/30022486/
3. Kottner J, et al. TEWL in healthy adults, original meta-analysis. Arch Dermatol Res. 2013. Meta-analysis, 167 studies, 50 skin areas. https://pubmed.ncbi.nlm.nih.gov/23341028/
4. Palma ML, et al. Effect of increased water intake on skin hydration and TEWL. Skin Res Technol. 2015. n=34 healthy women, 30 days, no control group described. https://pubmed.ncbi.nlm.nih.gov/26058417/
5. Fluhr JW, et al. Glycerol and barrier repair after tape stripping and SLS exposure. Acta Derm Venereol. 1999. 2 in vivo studies, 3- and 7-day follow-up; n not reported in abstract. https://pubmed.ncbi.nlm.nih.gov/10598752/
6. van Zuuren EJ, et al. Emollients and moisturisers for eczema. Cochrane Database Syst Rev. 2017. Systematic review, 77 RCTs, 6,603 participants. https://pubmed.ncbi.nlm.nih.gov/28166390/
7. Andrew PV, et al. Physiological-lipid multivesicular emulsion vs glycerine emulsion on barrier function. Br J Dermatol. 2025. Double-blind intra-participant trial, n=58, 28 days; funding not reported in abstract. https://pubmed.ncbi.nlm.nih.gov/40408261/
8. Ghadially R, Halkier-Sorensen L, Elias PM. Effects of petrolatum on stratum corneum structure and barrier recovery. J Am Acad Dermatol. 1992. Human volunteers, acetone disruption; n not reported in abstract. https://pubmed.ncbi.nlm.nih.gov/1564142/
9. Man MQ, Feingold KR, Thornfeldt CR, Elias PM. Ceramide, cholesterol and free fatty acid mixtures in barrier repair. J Invest Dermatol. 1996. Mostly murine, preliminary human data. https://pubmed.ncbi.nlm.nih.gov/8618046/
10. Zettersten EM, et al. Lipid mixtures and barrier recovery in aged skin. J Am Acad Dermatol. 1997. Aged mice plus aged human skin, n=6. https://pubmed.ncbi.nlm.nih.gov/9308554/
11. Spada F, et al. Ceramide-dominant cream and cleanser in moderate eczema. Dermatol Ther. 2021. RCT, 28 days; n not reported in abstract; sponsored by Ego Pharmaceuticals (manufacturer). https://pubmed.ncbi.nlm.nih.gov/33984185/
12. Tanno O, et al. Nicotinamide increases stratum corneum lipid biosynthesis. Br J Dermatol. 2000. In vitro keratinocytes plus topical human study (n not reported in abstract). https://pubmed.ncbi.nlm.nih.gov/10971324/
13. Raikou V, et al. Acetyl hexapeptide-3 and TEWL. 2017. n=24 volunteers, 60 days; design and funding not reported in our source notes. https://pubmed.ncbi.nlm.nih.gov/28150423/
14. Badenhorst T, et al. Physicochemical characterization and stability of GHK-Cu. Pharm Dev Technol. 2016. Laboratory study. https://pubmed.ncbi.nlm.nih.gov/25384620/
15. Mortazavi SM, Mohammadi Vadoud SA, Moghimi HR. GHK and GHK-Cu review. Bioimpacts. 2025. Narrative review. https://pubmed.ncbi.nlm.nih.gov/39963574/
16. Mortazavi SM, Moghimi HR. Skin permeability, a dismissed necessity for anti-wrinkle peptide performance. Int J Cosmet Sci. 2022. Narrative review. https://pubmed.ncbi.nlm.nih.gov/35302659/
17. Ridha Z, et al. GLP-1 receptor agonists and facial aging. Aesthet Surg J. 2024. Narrative review. https://pubmed.ncbi.nlm.nih.gov/38874170/
18. Barone M, et al. Skin and facial changes with GLP-1 receptor agonists. Aesthetic Plast Surg. 2026. Systematic review of 40 human studies. https://pubmed.ncbi.nlm.nih.gov/42162206/
19. Pu SY, et al. Hydrolyzed collagen and skin hydration and elasticity. Nutrients. 2023. Meta-analysis, 26 RCTs, 1,721 participants. https://pubmed.ncbi.nlm.nih.gov/37432180/
20. Myung SK, Park Y. Collagen supplements and skin aging. Am J Med. 2025. Meta-analysis, 23 RCTs, 1,474 participants. https://pubmed.ncbi.nlm.nih.gov/40324552/

Disclosure: This article is for general education and is not medical advice. It doesn't replace a consultation with a dermatologist or other qualified clinician. If you have persistent, painful, cracked or spreading skin symptoms, seek professional care. If you take a prescription medication, including a GLP-1 receptor agonist, talk to your prescriber before making changes. This article contains no affiliate links, and no brand paid for or reviewed it.

For educational purposes only; not medical advice. See our disclaimer and research method.