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Eczema: barrier first, and the food myths that do harm

Atopic eczema is a barrier problem before it is anything else. Which ingredients rebuild the barrier and which ones to remove from the bathroom, what the evidence says about vitamin D, evening primrose oil and probiotics, why cutting foods out without a diagnosis can create a new allergy, and the signs that need a doctor today.

This page describes what eczema is and what the evidence supports. It does not diagnose, and it does not tell you to start or stop any prescribed treatment. Skin that is weeping, crusting, spreading or painful, or eczema with fever, needs a clinician rather than a website.

What is actually going wrong

Atopic eczema is a barrier disease with an immune reaction on top. The outer layer of the skin is supposed to be a sealed wall of dead cells set in lipid mortar; in eczema that mortar is short of ceramides, the wall leaks water outward and lets irritants and allergens inward, and the immune system responds to what gets through. The itch that follows leads to scratching, scratching breaks the wall further, and the cycle sustains itself.

A meaningful minority of northern Europeans carry loss-of-function variants in the gene for filaggrin, a protein central to building that outer layer and to producing the skin's natural moisturising factor. Those variants are a strong risk factor for eczema, and they are notably common in northern European populations — which is part of why eczema, dry skin and winter cracking are such ordinary complaints around the Baltic. You cannot change the gene. You can substitute for what it fails to make, which is exactly what an emollient does.

The routine that has evidence behind it

The order matters, and it is the opposite of an acne routine. Nothing here exfoliates, brightens or resurfaces. The whole job is to put lipids and water back and to stop taking them away.

Three things to take out of the bathroom: fragrance, including essential oils and "natural" scents; anything preserved with Metilisotiazolinona, which is banned in leave-on products in the EU but still permitted in rinse-off ones; and exfoliating acids and scrubs on eczema-prone skin, which are the wrong tool entirely. Fragrance-free is a genuinely useful label; "unscented" can mean a masking fragrance was added.

Prescribed anti-inflammatory treatment is a separate matter from all of the above. Undertreating a flare out of fear of the treatment is a well-documented pattern that leaves people itching for months, and the person to resolve it with is the prescriber, not a comment section.

Food, supplements and the things people try

Elimination diets Can cause harm

This is the most important paragraph on the page. Removing foods from the diet on suspicion, without a proper allergy assessment, has two documented costs. It delays the treatment that works, and — more seriously — a food that has been excluded for months can provoke an immediate allergic reaction on reintroduction that did not exist before the exclusion. Add the nutritional cost to a growing child and the arithmetic is clearly negative. If food allergy is genuinely suspected, ask for assessment.

Evening primrose and borage oil Not supported

These were among the most popular supplements for eczema for decades. Systematic review of the randomised trials found no meaningful benefit over placebo, which is about as clear an answer as this field produces. Money better spent on emollient.

Vitamin D Mixed, deficiency-dependent

Trials have produced inconsistent results, with what benefit there is concentrated in people who were deficient to begin with. That caveat matters more at this latitude than most: sun exposure between autumn and spring in the Nordic and Baltic countries is not enough for skin synthesis, and winter deficiency is common. That makes vitamin D a reasonable thing to have tested and to discuss, and a poor thing to guess about. See the foods highest in vitamin D and the supplements reference.

Probiotics Weak and inconsistent

Trials of probiotics for treating established eczema have been inconsistent and mostly unimpressive, with strains, doses and outcome measures varying so much between studies that pooling them tells you little. The separate question of whether they prevent eczema in high-risk infants has its own uncertain literature and is a conversation for a paediatric clinician.

Hard water Association, not a fix

Living in a hard-water area is associated with eczema in children, and it is a reasonable hypothesis that mineral content plus soap makes washing harsher. Trials of installing water softeners have not, however, shown benefit for eczema that is already established. Adjusting how you wash is free; plumbing is not.

The Nordic winter problem

Cold outdoor air holds little water, indoor heating dries what is left, and the gap between a heated flat and a February street is the single most reliable eczema trigger in this part of the world. The practical adjustments are unglamorous: shorter and cooler showers, emollient applied while skin is still damp, a cotton layer between skin and wool, and accepting that a sauna feels wonderful and stings on broken skin — moisturise afterwards rather than skipping it. Nothing here is a treatment; all of it reduces how hard the treatment has to work.

When to see a clinician

• Today, if there are painful clusters of small punched-out sores, spreading quickly, especially with fever or feeling unwell. Eczema-damaged skin can be infected by the cold-sore virus and that is treated urgently.
• Promptly, for weeping, golden crusting, pustules or increasing pain, which suggest bacterial infection.
• If it is not controlled by regular emollients and whatever has been prescribed, or if it is disturbing sleep — for the person with eczema or for the parents.
• If severe eczema appears for the first time in an adult, which deserves assessment rather than assumption.
• If a product seems to be causing it: ask about patch testing rather than working through the shelf by trial and error. Contact allergy to a preservative or a fragrance can look exactly like eczema getting worse.

Sources: EU Cosmetics Regulation (EC) No 1223/2009 and its annexes, as published in the European Commission's CosIng database, for every statement about what is permitted, restricted or banned · opinions of the Scientific Committee on Consumer Safety (SCCS) and safety assessments of the Cosmetic Ingredient Review (CIR) for the concentration positions · standard dermatology reference material for mechanism, tolerability and contact-allergy patterns · checked 2026-09-06. Deep links are deliberately omitted where a stable public URL could not be confirmed.

Positions above reflect published systematic reviews and dermatology guidance: no benefit for evening primrose and borage oil, inconsistent results for probiotics and for vitamin D outside deficiency, and the documented risk of provoking immediate-type allergy after unnecessary food exclusion.

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