Vitamin D and Skin: The Deficiency Signs Written on Your Body

27 Sept

Written By Joey .

Vitamin D is described as the "sunshine vitamin", which does it a disservice — it is not really a vitamin at all, but a secosteroid hormone with receptors in almost every tissue in the human body, including the skin, the gut lining, immune cells, and the oral mucosa. When it is deficient — and a strikingly high proportion of the population is — the consequences are written across multiple systems at once. The skin is one of the most revealing places to read them, because vitamin D is both produced in the skin and required for the skin to function: barrier integrity, immune defence, wound healing, and inflammatory regulation all depend on it.^1,2

This is a subject close to the core of how I assess skin — as a readout of internal status rather than an isolated surface. This post covers what vitamin D actually does for the skin, the visible and systemic signs of deficiency (including what shows up on the tongue and in the mouth), and the evidence connecting low vitamin D to acne, eczema, impaired wound healing and scarring, immune dysfunction, and the gut microbiome.

◆ Quick Answer

What are the signs of vitamin D deficiency in the skin? Vitamin D deficiency is associated with worsened inflammatory skin conditions (eczema, acne, psoriasis), impaired wound healing and poorer scar quality, increased skin infections due to reduced antimicrobial peptide production, and dry, compromised skin barrier function. It can also produce oral signs — burning mouth sensation, dry mouth, and glossitis (tongue inflammation) — often alongside B-vitamin, iron, and zinc deficiencies. Because vitamin D regulates immune balance and the gut barrier, its deficiency contributes to the systemic inflammation that drives chronic skin disease from the inside.^1,2,3

What Vitamin D Actually Does for the Skin

Vitamin D's role in the skin extends far beyond its classical association with bone and calcium metabolism. The skin is unique in being both the site of vitamin D synthesis (UVB converts 7-dehydrocholesterol to vitamin D3) and a target organ dense with vitamin D receptors (VDR). Its documented functions in skin health include:

Barrier function: Vitamin D regulates the production of structural proteins and lipids that maintain the epidermal barrier. VDR and vitamin D binding protein levels are demonstrably lower in the epidermis of atopic dermatitis patients than in normal skin.⁴
Antimicrobial defence: Vitamin D drives the production of cathelicidin and other antimicrobial peptides — the skin's own antibiotics. This is a central mechanism in defending against skin infection and controlling the microbial imbalance seen in eczema.^2,5
Immune regulation: Vitamin D shifts the immune balance away from the pro-inflammatory Th2 and Th17 responses that drive atopic dermatitis and psoriasis, and toward regulatory T-cell (Treg) activity. It suppresses key inflammatory cytokines including IL-4, IL-13, IL-31, IL-33, and TSLP.⁶
Cell turnover: Vitamin D regulates keratinocyte proliferation and differentiation — which is why vitamin D analogues (calcipotriol) are an established topical treatment for psoriasis.³
Wound healing: Vitamin D is essential for efficient wound repair and the coordinated fibroblast activity that determines healing quality.^3,7

~50% of the global population is estimated to have insufficient vitamin D, with deficiency affecting up to 1 billion people worldwide — making it one of the most common and most overlooked nutritional contributors to chronic skin disease.¹

The Visible Signs of Vitamin D Deficiency

Vitamin D deficiency rarely produces one dramatic sign. More often it presents as a cluster of low-grade problems across several systems — which is precisely why it is so frequently missed. The skin and its associated structures are among the most revealing:

Skin barrier

Dry, rough, compromised skin

Impaired barrier lipid production leads to dryness, rough texture, and increased sensitivity — the skin loses water and becomes more reactive to irritants.⁴

Inflammation

Worsening eczema & dermatitis

Low vitamin D correlates with greater atopic dermatitis severity — driven by reduced barrier function, lower antimicrobial defence, and unrestrained Th2 inflammation.^6,8

Infection

Frequent skin infections

Reduced cathelicidin production impairs the skin's antimicrobial defence, allowing overgrowth of S. aureus and increased susceptibility to bacterial and fungal skin infections.^2,5

Repair

Slow wound healing & poor scars

Delayed wound closure and poorer scar quality result from impaired fibroblast coordination and reduced antimicrobial protection during healing.^3,7

Oral mucosa

Burning mouth & tongue changes

Burning mouth sensation, dry mouth, and glossitis (tongue inflammation) — vitamin D deficiency was found in 15% of burning mouth syndrome patients.^9,10

Hair & scalp

Hair thinning & scalp issues

Vitamin D receptors are essential for the hair follicle cycle; deficiency is associated with hair loss (including alopecia areata) and scalp inflammation.³

The Tongue and Mouth: An Overlooked Window

The oral mucosa is one of the most metabolically active tissues in the body, with rapid cell turnover that makes it an early indicator of nutritional status. Changes in the tongue and mouth are among the most under-recognised signs of micronutrient deficiency — and vitamin D is part of a cluster that shows up here.

📄 Vitamin D and Burning Mouth Syndrome — Case-Control & Review Evidence

Vitamin D deficiency was confirmed in 15% of secondary burning mouth syndrome patients in screening studies. In a documented case series, patients presenting with burning mouth sensation had vitamin D deficiency (as low as 18.8 nmol/L) alongside objective oral dryness and fungal hyphae — suggesting hypovitaminosis D, xerostomia, and candidal overgrowth as interacting precipitating factors. Vitamin D is thought to play a role in axonogenesis and sensory nerve transmission in peripheral neurons, offering a mechanism for the burning sensation, with the effect appearing particularly relevant in patients with concurrent diabetes and dry mouth.^9,10

Geographic Tongue, Glossitis, and the Deficiency Cluster

Vitamin D rarely acts alone in oral signs. The tongue changes associated with nutritional deficiency reflect an overlapping cluster:

Oral / Tongue Sign	Most Associated Deficiencies	Appearance
Burning mouth sensation	Vitamin D, B1, B2, B6, B12, zinc, iron	Burning of tongue/lips/mouth without visible cause
Atrophic glossitis	B12, folate, iron	Smooth, shiny, beefy-red tongue; loss of papillae
Geographic tongue	B2, zinc, iron, B12 (associations)	Map-like red patches with white borders that migrate
Angular cheilitis	B2, B6, B12, iron	Cracking/inflammation at the corners of the mouth
Recurrent mouth ulcers	B12, folate, iron, vitamin D	Repeated aphthous ulceration

The clinical point: Oral and tongue signs are rarely caused by a single deficiency, and they overlap heavily with iron, zinc, and B-vitamin status. Geographic tongue in particular is most consistently linked to B2 (riboflavin), zinc, and iron rather than vitamin D specifically — though vitamin D sits within the same nutritional picture. When these signs appear, they warrant a full nutritional assessment rather than assuming a single cause. This is exactly the kind of internal readout that a functional skin and nutritional assessment is designed to catch.^10,11,12

Vitamin D and Acne

The relationship between vitamin D and acne is increasingly well-documented. Acne is an inflammatory condition — not merely a problem of oil and bacteria — and vitamin D's immunomodulatory and antimicrobial roles place it directly within acne's pathophysiology.

📄 Wang, Zhou & Yan — Vitamin D Status and Supplementation in Acne (Systematic Review & Meta-Analysis)

This systematic review and meta-analysis examined vitamin D status in acne patients and the effect of supplementation. Acne patients were found to have lower serum vitamin D levels than controls, and vitamin D deficiency correlated with acne severity. Supplementation studies indicated improvement in acne with correction of deficiency — supporting vitamin D as a modifiable contributing factor. The proposed mechanisms include vitamin D's suppression of the inflammatory cytokines driving the acne lesion, its regulation of sebocyte activity, and its antimicrobial effect against Cutibacterium acnes.¹³

This connects acne to the broader picture of internal drivers I discuss in the context of insulin resistance and the gut. Vitamin D deficiency is one more systemic input that lowers the threshold for the inflammatory cascade that produces acne — which is why correcting it is worth assessing as part of a complete approach rather than treating the skin surface alone.

Vitamin D, Eczema, and the Skin Microbiome

Atopic dermatitis (eczema) has the strongest and best-characterised relationship with vitamin D of any skin condition — and it is where the gut-skin-immune connection becomes clearest.

📄 Vitamin D in Atopic Dermatitis — Disease Severity and Skin Microbiome (2023–2025 reviews)

Atopic dermatitis is characterised by skin barrier dysfunction, immune dysregulation, and microbial dysbiosis — specifically Staphylococcus aureus overcolonisation and reduced bacterial diversity. Vitamin D influences all three: it reinforces the barrier, drives antimicrobial peptide production that controls S. aureus, and shifts immune balance away from the Th2 response. Multiple studies confirm that lower serum vitamin D correlates with greater eczema severity, and that maternal vitamin D levels correlate with infant eczema risk and cord-blood FOXP3 (Treg) expression. Commensal skin bacteria such as Staphylococcus epidermidis also generate ceramides and short-chain fatty acids that stabilise the skin lipid barrier — linking the microbiome directly to barrier function.^6,8,14

The Gut Microbiome Connection

Vitamin D's influence on the skin is inseparable from its role in the gut. Vitamin D receptors line the intestinal epithelium, where vitamin D maintains the gut barrier integrity and regulates the microbiome. Deficiency contributes to intestinal permeability and dysbiosis — allowing the systemic inflammation and immune dysregulation that manifests in the skin. This is the gut-skin axis in action: vitamin D is one of the key molecules operating in both compartments simultaneously, which is why its deficiency shows up as both gut and skin problems at once.^2,14

Vitamin D, Wound Healing, and Scarring

Wound healing is one of vitamin D's most clinically significant skin functions — and one with direct relevance to scarring outcomes, including after procedures.

Vitamin D contributes to each phase of wound repair. During the inflammatory phase, it drives antimicrobial peptide production (cathelicidin) that protects the wound from infection. During the proliferative and remodelling phases, it supports the fibroblast activity that produces and organises collagen. Fibroblasts are central to both wound closure and to how the resulting scar is structured — and their function is vitamin D-dependent.^3,7

Why Vitamin D Deficiency Impairs Healing and Scar Quality

Reduced antimicrobial defence: Lower cathelicidin means higher wound infection risk — and infected wounds heal slower and scar worse.³
Impaired fibroblast coordination: Vitamin D regulates the dermal fibroblasts responsible for collagen production and organised tissue repair.⁷
Unregulated inflammation: Without vitamin D's immunomodulation, the prolonged inflammatory phase of healing can drive poorer, more fibrotic scar outcomes.^3,6
Delayed closure: Slower re-epithelialisation extends the healing window and the opportunity for complications.³

This is directly relevant to any procedure that relies on controlled wound healing to produce a good result — including collagen induction therapy and treatments for acne scarring. The skin's ability to heal and remodel is only as good as its nutritional foundation. Correcting a vitamin D deficiency before undertaking treatments that depend on the wound-healing response is a sensible, evidence-aligned step that most patients are never advised to take.

✦ Functional Dermal Repair & Assessment

Optimising the internal foundation — including vitamin D and the wider nutritional picture — before and alongside treatments that rely on wound healing is part of a functional approach to skin repair and scar management, rather than treating the surface in isolation.

Vitamin D and the Immune System

Underlying every one of vitamin D's skin effects is its role as an immune regulator. Nearly all immune cells express the vitamin D receptor, and vitamin D acts as a brake on excessive inflammation while supporting antimicrobial defence. In the skin this dual role is critical: it must simultaneously defend against pathogens and avoid the chronic inflammation that drives disease.

Vitamin D deficiency has been linked to an increased risk of autoimmune and inflammatory skin conditions — including psoriasis, eczema, alopecia areata, and vitiligo — through its loss of immunomodulatory control. It suppresses the Th1, Th2, and Th17 pathways that drive these conditions while supporting the regulatory T cells that keep the immune response in check. When vitamin D is low, that regulatory brake is weakened, and the immune system is more prone to the dysregulated activity that manifests as chronic skin disease.^1,3,6

How much vitamin D do you need for healthy skin?

For skin and immune health, most functional and clinical guidance targets a serum 25(OH)D level in the range of 75–125 nmol/L (30–50 ng/mL) — higher than the minimum threshold set purely for bone health. The exact dose to achieve this varies considerably between individuals based on baseline level, body weight, sun exposure, skin type (higher melanin reduces UVB synthesis), gut absorption, and genetics. Because vitamin D is fat-soluble and can accumulate, supplementation is best guided by a blood test rather than guessed — both to confirm deficiency and to avoid excess. Testing 25(OH)D is a simple, inexpensive step that removes the guesswork, and it is one of the most useful single markers in a skin-focused nutritional assessment.^1,3

Can vitamin D deficiency cause skin problems even with a good skincare routine?

Yes — because vitamin D deficiency drives skin problems from the inside, no topical routine can compensate for it. Barrier function, antimicrobial defence, immune regulation, and wound healing all depend on adequate vitamin D at the cellular level, and these cannot be replicated by products applied to the surface. A patient can use an excellent skincare regimen and still experience persistent eczema, recurrent breakouts, poor healing, or a compromised barrier if an underlying deficiency is left uncorrected. This is the central principle of assessing skin as a readout of internal health: the surface reflects the systemic foundation, and when a skin condition resists topical management, the internal drivers — vitamin D among them — are where the answer usually lies.^2,4,6

Frequently Asked Questions: Vitamin D and Skin

Can low vitamin D cause acne?

Evidence indicates acne patients have lower serum vitamin D than controls, and that deficiency correlates with acne severity. Vitamin D contributes to acne through its anti-inflammatory action, its regulation of sebocyte activity, and its antimicrobial effect against C. acnes. Correcting a documented deficiency has shown benefit in supplementation studies. Vitamin D is best understood as one modifiable contributing factor within acne's multifactorial picture — worth assessing and correcting, but not a standalone cure.¹³

Does vitamin D help eczema?

The evidence is strongest here. Lower serum vitamin D consistently correlates with greater eczema severity, and vitamin D influences the three core features of atopic dermatitis: it reinforces the skin barrier, drives antimicrobial peptides that control S. aureus overgrowth, and shifts immune balance away from the Th2 inflammation that drives the disease. Supplementation evidence in eczema is promising though somewhat inconsistent, with the greatest benefit seen in patients who are genuinely deficient — which is why testing matters.^6,8

What does the tongue look like with vitamin D deficiency?

Vitamin D deficiency can contribute to a burning sensation in the tongue and mouth (burning mouth syndrome), often with dry mouth, without an obvious visible change. Where visible tongue changes occur — a smooth, red, or inflamed tongue (glossitis), or map-like patches (geographic tongue) — these are more strongly associated with B12, folate, iron, riboflavin (B2), and zinc deficiencies, which frequently coexist with low vitamin D. Because these signs overlap, tongue and mouth changes warrant a full nutritional assessment rather than assuming a single cause.^9,10,11,12

Does vitamin D affect wound healing and scarring?

Yes. Vitamin D supports each phase of wound repair — antimicrobial protection during the inflammatory phase, and fibroblast-driven collagen production during remodelling. Deficiency is associated with delayed wound closure and poorer scar quality. This is clinically relevant before any procedure that relies on the wound-healing response, such as microneedling or acne scar treatments — optimising vitamin D beforehand supports a better healing and scar outcome.^3,7

Should I get my vitamin D tested?

If you have a persistent skin condition that resists topical treatment — eczema, acne, poor healing, recurrent infections — or oral signs like burning mouth or a sore tongue, a 25(OH)D blood test is a simple, worthwhile step. Given how common deficiency is (affecting up to half the population) and how central vitamin D is to skin function, it is one of the most useful single markers to check. Testing also allows supplementation to be dosed accurately and safely, rather than guessed.^1,3

Is a nutrient deficiency showing up in your skin?

A functional skin and nutritional assessment — including vitamin D and the wider micronutrient picture — can identify the internal drivers behind persistent skin conditions that topical treatment alone hasn't resolved.

Book a functional skin consultation →

References

Alshahrani F, Aljohani N. Vitamin D: deficiency, sufficiency and toxicity. Nutrients. 2013;5(9):3605–3616; and: The beneficial roles of vitamin D in skin health. Appl Sci. 2025;15(2):796. doi:10.3390/app15020796.
Vitamin D and skin disorders: bridging molecular insights to clinical innovations. PMC. PMC12275319. 2024.
Vitamin D deficiency and the pathophysiology of skin disorders — immunomodulation and dermatological etiology. ClinicSearch / clinical review. 2023.
Lu J, et al. Vitamin D attenuates DNCB-induced atopic dermatitis-like lesions by inhibiting immune response and restoring skin barrier function (reduced VDBP/VDR in AD epidermis). Int Immunopharmacol. 2023.
Gut-skin axis: unraveling the role of vitamins in skin health — antimicrobial peptides and wound healing. IntechOpen. 2025.
Molecular insights into the role of vitamin D in atopic dermatitis: pathogenesis, diagnosis, and emerging therapies. Front Immunol / PubMed. 2026. PMID:41983140.
Boraldi F, et al. The role of fibroblasts in skin homeostasis and repair. Biomedicines. 2024;12:1586; and Wang J, et al. Immune function of dermal fibroblasts. Exp Dermatol. 2023;32:1326–1333.
McCarthy RL, et al. Vitamin D deficiency and atopic dermatitis severity in a Bangladeshi population living in East London: a cross-sectional study. Skin Health Dis. 2024;4(3):e358. doi:10.1002/ski2.358.
Hypovitaminosis D, objective oral dryness, and fungal hyphae as precipitating factors for secondary burning mouth syndrome. Heliyon. 2023. S2405844023071621.
Micronutrients status as a contributing factor in secondary burning mouth syndrome: a review of the literature. PMC. PMC10883099. 2024.
Determining salivary and serum levels of iron, zinc and vitamin B12 in patients with geographic tongue. PMC. PMC6904920. 2019.
Oral manifestations of vitamin B12 deficiency (glossitis, glossodynia, burning). PMC. PMC11254220. 2024.
Wang M, Zhou Y, Yan Y. Vitamin D status and efficacy of vitamin D supplementation in acne patients: a systematic review and meta-analysis. J Cosmet Dermatol. 2021;20(12):3802–3807.
Vitamin D in atopic dermatitis: role in disease and skin microbiome. PMC. PMC12655013. 2025.

Joey .