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Vitamin D

John Montgomery6 min read

Vitamin D

Vitamin D (cholecalciferol, D3) is a fat-soluble vitamin made in the skin in sunlight and found in oily fish, fortified foods and supplements. Its blood marker is 25-hydroxyvitamin D, or 25(OH)D. The case for using it in Atopic Dermatitis rests on several observations. Eczema is more common at higher latitudes and often flares in winter. Vitamin D helps regulate skin-barrier proteins (see Skin Barrier Dysfunction) and triggers antimicrobial peptides such as cathelicidin that may reduce skin infection, including with Staphylococcus aureus. And people with eczema tend to have lower levels (Hattangdi-Haridas 2019; Camargo 2014). In a 2019 meta-analysis of 11 case-control studies, people with eczema had serum 25(OH)D about 14 nmol/L lower than healthy controls, and in the paediatric studies alone children with eczema were about 16 nmol/L lower (95% CI −31 to −1). The authors called children with eczema a possible “at-risk group” for insufficiency. In a Toronto study of 77 children, lower vitamin D levels went with more severe eczema (P = .015; Lara-Corrales 2019). No traditional-remedy history applies: this is a modern nutritional hypothesis, although “more sun in summer” is a long-standing parent observation.

Vitamin D [part-of] Herbal and Home Remedies for Eczema Vitamin D [relates] Skin Barrier Dysfunction Vitamin D [relates] Staphylococcus aureus Vitamin D [treats] Atopic Dermatitis

Key trials in children. The best-known paediatric RCT is Camargo et al. (J Allergy Clin Immunol, 2014). It enrolled 107 Mongolian children aged 2–17 (mean age 9) whose eczema worsened in winter, in Ulaanbaatar at latitude 48° N, where winter deficiency is common. They took 1,000 IU a day of cholecalciferol or placebo for one month, and all families also received emollients and skin-care education. EASI scores improved more on vitamin D (adjusted change −6.5 vs −3.3, P = .04), the investigator’s global assessment also favoured vitamin D (P = .03), and there were no adverse effects. It followed a small Boston pilot in 11 children (Sidbury 2008), whose EASI improvement was not statistically significant (Schäfer). By contrast, a Toronto double-blind RCT (Lara-Corrales 2019) gave 2,000 IU/day or placebo for 3 months to 45 children with low vitamin D (<72.7 nmol/L). Severity improved by the same amount in both groups (15.35 vs 15.13 points, P = .7).

Conflict: [Camargo et al., J Allergy Clin Immunol, 2014] says 1,000 IU/day for one month significantly improved winter-related eczema in children (EASI −6.5 vs −3.3). [Lara-Corrales et al., J Cutan Med Surg, 2019] says 2,000 IU/day for three months in vitamin-D-insufficient children made no difference to severity (P = .7). Unresolved — add to open_questions.

Vitamin D [relates] EASI

Strength of evidence: contested. The pooled analyses lean positive, but they rest on small, short and mixed trials. Hattangdi-Haridas et al. (Nutrients, 2019) reviewed five trials: SCORAD fell by 11 points in a meta-analysis of three RCTs (95% CI −13 to −9) and by 21 points in repeated-measures studies, at about 1,500–1,600 IU/day. This beats the 9-point minimal clinically important difference, but most participants started out deficient and had mild to moderate eczema. NCCIH cites this review as showing “clinically relevant improvements”. Nielsen et al. (Nutrients, 2024) pooled 11 RCTs with 686 children and adults and found a moderate effect (standardised mean difference −0.41, 95% CI −0.67 to −0.16) with substantial heterogeneity (I² 58%). They called for larger, longer trials. Older reviews were less positive. The 2012 Cochrane review of dietary supplements (Bath-Hextall) found “no convincing evidence” for any supplement, vitamin D included, and the 2014 American Academy of Dermatology guideline found “inconsistent to no evidence” for vitamin D (NCCIH).

Conflict: [Nielsen et al., Nutrients, 2024; Hattangdi-Haridas et al., Nutrients, 2019] say vitamin D supplementation significantly reduces eczema severity in children and adults. [Bath-Hextall et al., Cochrane, 2012; AAD guideline 2014 via NCCIH] say there is no convincing, or inconsistent to no, evidence to recommend vitamin D for eczema. The newer meta-analyses post-date the Cochrane search (2010). Unresolved — add to open_questions.

Cochrane [contradicts] Vitamin D American Academy of Dermatology [contradicts] Vitamin D

Toddler safety. Vitamin D is a real drug at high doses. The Cochrane review warns that “high doses of vitamin D may give rise to serious medical problems”. The doses used in trials, 1,000–2,000 IU (25–50 µg) a day, approach the European Food Safety Authority’s tolerable upper intake level for children aged 1–10 (50 µg/day) and exceed the infant limits (25 µg/day under 6 months; 35 µg/day at 6–12 months, EFSA 2018). The 2019 meta-analysis therefore advises blood monitoring for children on 1,500–1,600 IU/day and says “infants should definitely not be given” that dose (Hattangdi-Haridas 2019). For a toddler, the sensible approach is to check whether they are deficient, especially in winter, with dark skin, little sun, or a restricted diet, and to give doses under medical advice rather than adult-strength capsules. Vitamin D is an add-on at most. It does not replace Emollient Therapy or Topical Corticosteroids.

Unsupervised food elimination diets cause nutritional gaps

Cutting out cow’s milk or several foods to “cure” eczema raises the risk of too little calcium, vitamin D, iodine, protein and energy in young children (Dobrijević et al., Children, 2026). Only exclude foods after a confirmed Food Allergy diagnosis, with a dietitian, and ask about vitamin D cover. See Elimination Diets.

Elimination Diets [causes] Vitamin D Vitamin D [relates] Food Allergy

What parents report (evidence: anecdotal). Parents often notice that eczema is better in summer and worse in winter, a pattern that fits the winter-related eczema enrolled in the Camargo trial. Summer also brings more humidity and less central heating, so the link is not specific to vitamin D. No reliable parent-forum data were collected for this note. In the Reddit threads reviewed for Evening Primrose Oil, posters often took several supplements together (for example a multivitamin plus EPO), so it is impossible to tell which one helped.

Vitamin D [relates] Evening Primrose Oil Vitamin D [relates] Fish Oil and Omega-3

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