Journal September 27, 2026 6 min read

How the Skin Barrier Changes with Age

A research overview of age-related changes in skin barrier function, covering transepidermal water loss, NAD+ decline, sphingolipid metabolism, and the models used to study barrier integrity.

peptides-pro Editorial

The skin barrier is the outermost compartment of the epidermis, the stratum corneum, a lipid-protein matrix that regulates transepidermal water loss (TEWL) and restricts entry of exogenous substances. In the research literature it is also referred to as the epidermal permeability barrier or cutaneous barrier. Its functional readouts are biophysical rather than structural: TEWL, stratum corneum hydration, surface pH, and erythema index. The work described below centres on the sphingolipid and ceramide pathway of the stratum corneum, together with the nicotinamide adenine dinucleotide (NAD+) salvage pathway, both of which have been examined in relation to barrier competence.

Age-related change in this compartment is not a single event. Barrier lipids, corneocyte turnover, and the redox environment of epidermal cells shift on different timelines, and the direction of change depends on the site sampled and the population studied. Much of the mechanistic work has been done in animal models or in vitro, and that limitation is stated where it applies.

Research Studies

Vernix caseosa and barrier integrity in newborns

Vernix caseosa is a naturally occurring, white, creamy substance covering the skin of newborns at birth, formed during the last trimester. A registered trial is examining retention of vernix caseosa in newborns for primary prevention of atopic dermatitis, on the basis that genetic and environmental factors related to skin-barrier integrity and the skin microbiome during early life contribute to disease development [1]. The population is newborns; the outcome under study is prevention of atopic dermatitis, not barrier measurement in adults.

Peristomal and non-peristomal barrier characterisation in people with a stoma

An exploratory study is collecting preliminary data on peristomal and non-peristomal skin barrier characterisation in people living with a stoma. It asks whether barrier characterisation differs between peristomal and non-peristomal skin, whether peristomal barrier function differs by stoma type (colostomy, ileostomy, urostomy), and whether stoma type or function influences peristomal barrier characterisation. Participants attend a one-hour appointment and undergo non-invasive skin procedures [2]. This is a site-comparison design, not an age-comparison design.

Niacinamide riboside and skin NAD+ in aged skin

Niacinamide riboside (topical NR, also known as nicotinamide riboside) is an endogenous compound and a precursor to the co-enzyme nicotinamide adenine dinucleotide (NAD+). Work cited in a registered trial reported that skin NAD+ levels were negatively correlated with age in both males and females, and that aged skin was correlated with an increase in DNA damage. On that basis, the trial proposes that supporting skin NAD+ with precursors such as NR may be a strategy relevant to DNA damage associated with signs of skin aging, and is evaluating topical NR on signs of facial skin aging [4]. The correlation was observed in human skin; the proposed intervention is under test.

Collagen peptides and barrier function in women with dry, sensitive skin

A clinical study is testing whether two different doses of collagen-derived peptides taken for three months improve facial skin barrier integrity in women with dry, sensitive skin, compared with placebo [8]. The population is adult women with a defined skin phenotype, and the comparator is placebo. Results are not yet reported in the evidence available here.

AP collagen peptides in a mouse model of oxazolone-induced atopic dermatitis

Atopic dermatitis is a chronic, relapsing inflammatory skin disorder characterised by impaired skin barrier function and Th2-mediated immune responses. Collagen tripeptide (CTP) has been reported to improve skin hydration and barrier function. In one study, AP collagen peptide (APCP), which contains CTP, was evaluated for effects on skin hydration and inflammatory responses in an oxazolone-induced AD-like model using hairless mice, with skin hydration and transepidermal water loss measured [5]. This finding is animal-only and should not be extrapolated to human barrier physiology.

Phytoceramide production and sphingolipid pathway engineering

Phytoceramides are sphingolipids that support skin barrier integrity and hydration. Because their structures are intricate and their natural abundance is low, scalable production is difficult. One study applied integrated metabolic engineering and lipidomics in Saccharomyces cerevisiae, using three strategies: overexpression of SUR2 (sphinganine C4-hydroxylase) to boost phytosphingolipid formation; deletion of SCS7 (ceramide α-hydroxylase) to redirect flux toward non-hydroxylated phytoceramides; and overexpression of ISC1 [7]. This is a microbial production study, not a human barrier study.

Curcumin delivery and skin permeation in psoriasis models

Curcumin is administered cutaneously for psoriasis, but poor skin permeability and retention limit efficacy. One study fabricated mussel adhesion protein (MAP)-modified curcumin-loaded ethosomes (Cur-MAP-Es) to enhance permeation and retention within skin. The average particle size was 197.17 nm and encapsulation efficiency was 90.84%, with spherical morphology reported [6]. The work addresses topical delivery across a compromised barrier; it does not establish an age-related change in barrier function.

Psoriasis transcriptomics and barrier dysfunction

Psoriasis is a chronic immune-mediated inflammatory skin disease characterised by epidermal hyperproliferation, skin barrier dysfunction, and immune dysregulation. One study used the psoriasis transcriptomic dataset GSE14905 from the Gene Expression Omnibus, together with psoriasis-related genes and traditional Chinese medicine compound prescriptions, applying differentially expressed gene analysis and functional enrichment [3]. Barrier dysfunction here is a disease-associated feature, not an aging one.

Comparison of reported barrier-relevant measures

Study	Population or model	Barrier-relevant measure
Vernix caseosa retention [1]	Newborns	Atopic dermatitis incidence (primary prevention)
Peristomal barrier study [2]	People living with a stoma	Peristomal vs non-peristomal barrier characterisation
Topical niacinamide riboside [4]	Adults, facial skin aging	Skin NAD+ correlation with age; DNA damage
Oral collagen peptides [8]	Women with dry, sensitive skin	Facial skin barrier integrity vs placebo
AP collagen peptides [5]	Hairless mice, oxazolone-induced AD-like model	Skin hydration, transepidermal water loss

Additional reports in the evidence base describe topical regimens combining niacinamide, Pro-Xylane, and panthenol after laser procedures [9], mixed-culture ferment extracts with tripeptide GHK-Cu [10], hydrogel facial masks in sensitive skin [11], and carboxymethyl beta glucan in skin repair [12]. These are noted for completeness; they are not the basis of any section above.

If you are reading this for personal health reasons

The materials described here are sold for laboratory research use only. We do not provide dosing information, medical guidance, or recommendations for personal use. Anyone considering a compound for themselves should speak to a licensed clinician.