Stubborn eczema sometimes has a metal behind it, one you eat, wear and carry in your mouth. This post walks that idea end to end. What nickel allergy is as a diagnosis, why food nickel numbers move around, where filaggrin fits, and what the histidine, zinc and vitamin D research found.
The short answer up front. Nickel is the leading cause of contact dermatitis, a small share of nickel-sensitized people react systemically to dietary nickel, and that reaction shows up on skin and in the gut. Filaggrin is a separate, well-mapped barrier story. The interesting claim is that the two meet, and that's a hypothesis worth understanding rather than a settled mechanism.
The thesis belongs to Andra Sitoianu, who writes The Bioavailable Naturopath on Substack. She's a certified naturopath, and her article Heavy Metals, Filaggrins, and Eczema asks it in its subtitle: is a nickel sensitivity starving your skin of its own moisturizer? One limit, plainly. That article sits behind her paywall and only the opening story is public, so nothing here reconstructs her argument. The rest is built from her free nickel posts, her public thread and the peer-reviewed literature.
Where this comes from. This post draws on the public writing of Andra Sitoianu, The Bioavailable Naturopath, in particular From Mouth to Microbiome and Heavy Metals, Filaggrins, and Eczema. We paraphrase her framing, add the general research, and link her posts so you can read her in her own words; her paid guides carry her full protocols. Educational content, not medical advice.
The thesis, and where the public part stops
Her framing is that a barrier protein and an environmental metal are two halves of one picture, and that a nickel-sensitized immune system can keep a barrier from doing its job. The visible part of that article is a personal story: her son at five months old in 2018, oozing patches, sleepless nights, scratching until he bled, and a pediatrician offering blood work and one option. Then the paywall.
So I'll say what's fair to say. That question is a good one. It hasn't been answered by a trial that puts nickel avoidance and filaggrin measurement in the same study. What exists is solid evidence on each side of the equation separately, and that's what the rest of this post is.
Filaggrin, in one paragraph
Filaggrin is a protein that binds keratin filaments together in the outer layer of skin, and when it breaks down it releases the small molecules that make up natural moisturizing factor, including histidine derivatives that hold water inside corneocytes. Loss-of-function variants in the filaggrin gene are one of the strongest known risk factors for atopic dermatitis. That's the whole mechanism in a sentence, and it deserves more room than that, which is why it has its own post: barrier repair 101 covers lipids, filaggrin and NMF properly.
Systemic nickel allergy syndrome, in the careful version
This is the real clinical entity behind the food-nickel conversation, and it's narrower than the internet version. Systemic nickel allergy syndrome means systemic reactions, skin and gastrointestinal, to eating nickel-rich food in people who already have nickel allergic contact dermatitis. In a series of 145 patients with suspected SNAS who underwent oral nickel challenge, the 98 who challenged positive presented essentially with skin and gut symptoms, while dizziness, headache and similar complaints were never provoked by the challenge itself.
Two things follow. The diagnostic gold standard is the oral nickel challenge, done by a clinician, with a structured low-nickel diet alongside it. And a symptom checklist is not a diagnosis, which is why I'm not printing one, and why the self-check in her free post is described here rather than reproduced.
For scale: across 1,696 consecutive patients at four Italian allergy units, SNAS was confirmed in 98, about 5.78%. That's a clinic population, not a community rate. The same paper carries the wider point: nickel is the leading cause of contact dermatitis, and dietary nickel, mostly from plant foods, can provoke or worsen eczema and systemic contact dermatitis in some sensitized people.
The exposure audit
Andra's practical move is to list where nickel gets in before doing anything else, and that's a genuinely useful exercise even if you never change your diet. Here's the audit, with the honest status of each lane.
| Lane | What it looks like | What's established |
|---|---|---|
| Jewelry and hardware | Earrings, watch backs, jean buttons, belt buckles, zips | Contact dermatitis from skin contact is the classic, well documented route |
| Dental and orthodontic metal | Stainless brackets, nickel-titanium wires, some crowns and partials | Appliances raise salivary nickel early in treatment. Full version in the mouth post |
| Cookware and acid | Long contact between acidic food and stainless steel, storing leftovers in it | Cooking acidic food in stainless can raise the nickel content of the food |
| Diet | Cocoa, soy and legumes, nuts, whole grains, oats, some teas, canned food | Food is a major nickel source, but content varies by soil and processing |
The dental lane is the one people skip and the one she writes about most. It also carries the firmest boundary in this whole post: That's a conversation with your dentist about materials, and nobody should be pulling hardware out of their mouth on their own. The measurements and the questions to ask sit in the oral microbiome and dental metals post.
Why no low-nickel food list is a fixed table
Her own two posts don't agree with each other about lettuce, which is a useful illustration rather than a gotcha. Food nickel varies with soil, processing and cookware, so any list is an approximation of an approximation.
The dermatology review cited for this is Sharma's low nickel diet paper, and its numbers are worth knowing. An average diet supplies roughly 300 to 600 micrograms of nickel a day, with reported mean intakes of 120 to 210 micrograms in the UK, 130 in Finland and 170 in the United States. Higher-nickel foods listed include cocoa, soya beans, oatmeal, nuts, almonds, legumes, whole grains, tea and canned foods; lower-nickel foods include polished rice, refined wheat, corn products, eggs, poultry, most fish, milk, potatoes, cabbage and citrus.
Two caveats from the same review, both load bearing. Cooking acidic food in stainless steel can raise the nickel content of the food by dissociation from the alloy. And its conclusion is that a careful low-nickel diet leads to fewer and milder flare-ups in nickel-sensitive patients, not that it clears dermatitis.
One note of food literacy, since this is a tallow company and the question comes up: the lower-nickel side of these lists is mostly animal foods, eggs and simple starches, and familiar cooking fats including butter, ghee, olive oil and tallow sit on it. That's a fact about food. It says nothing about what a balm does, and I'd rather you have it than not.
Histidine, with the real numbers
This is where her public thread has been most influential, and where the numbers need care. The study everyone is pointing at is Tan and colleagues, 2017: a randomized, double blind, placebo controlled crossover pilot in 24 adults with atopic dermatitis, 21 of whom completed it, taking 4 g of oral L-histidine a day in a morning drink for eight week periods. Physician-scored SCORAD fell 34% at week 4 and 32% at week 8, patient-scored POEM fell 39% at both points, and the placebo produced no benefit.
Those are two different instruments, not one 39% result, and the comparison with a mid-potency topical steroid is a comparison the authors make against published figures rather than a head-to-head trial. The paper's own stated limitation is its size. That's still an interesting pilot, and it's worth reading as research rather than as a dose I'd suggest to anyone. The mechanism, why histidine and filaggrin and NMF belong in the same sentence, is in barrier repair 101.
Zinc, metallothionein and where her framework starts
Zinc matters for skin on its own terms. The NIH zinc fact sheet puts the RDA at 11 mg a day for adult men and 8 mg for women with a tolerable upper limit of 40 mg, names oysters as the densest source at about 32 mg per 3-ounce serving against 3.8 mg for beef sirloin, and lists skin among the systems affected by deficiency.
Metallothionein is the protein at the center of her nickel argument. What's established: metallothioneins are small cysteine-rich proteins that buffer and deliver zinc and copper, and high zinc concentrations induce them. That's the real basis for "zinc status governs metallothionein". What the review doesn't establish is that eating more zinc makes a person excrete nickel. She also works from a hair tissue mineral analysis tradition associated with Paul Eck and Lawrence Wilson, in which restoring minerals displaces toxic metals: that's her cited framework, not consensus toxicology, and I'm noting it rather than building on it.
Vitamin D, and her clinical notes
Vitamin D has the better evidence of the supplement group. A meta-analysis of 16 studies found people with atopic dermatitis had lower 25-hydroxyvitamin D than controls by a mean of 14 nmol/L, and pooling three supplementation trials, vitamin D lowered SCORAD by 11 points at a mean weighted dose of about 1,500 to 1,600 IU a day, which clears the 9 point minimal clinically important difference. Three trials is a thin base, and the observational half shows association rather than cause.
Where her clinical notes line up with that: asked on X about a severe eczema case, she declined the pearl powder that was suggested and pointed instead to L-histidine, zinc, vitamin D3, a low-nickel diet, and testing for fungal infection. One nuance, since her older writing gets mixed in: she has a separate 2023 thread about pearl powder for general skin, a different context and not part of an eczema stack. The fungal testing point is the one I'd underline, because it sends a person to a clinician who can actually test.
Comfort for itchy, dry patches, and where a clinician takes over
None of the above is what you do at 2am when skin is itching. Emollients are standard supportive care between flares in dermatology guidelines, fragrance and preservatives are common irritants, and simple is easier to troubleshoot than complicated. Here's what a balm does: it sits on the surface, slows water loss, and makes tight itchy skin more comfortable. It doesn't change filaggrin or remove a metal, and it isn't a treatment for eczema.
The clinician line, in plain words: eczema that's weeping, infected, spreading fast, suddenly worse or near the eyes belongs with a doctor. Nickel allergy is diagnosed by patch testing and oral challenge, not by a quiz, so if you suspect a food connection the person to talk to is an allergist or a dermatologist who can test rather than guess.
I've cut our unscented recipe down more times than I've added to it. Bare Silk ended at five ingredients with no water in the jar, which means no preservative system, because everything I left out is one fewer thing for reactive skin to argue with.
If you want one jar for itchy dry patches while you work through the rest of this, Bare Silk Unscented at $34 is the one I'd hand you: no fragrance, no essential oils, the shortest label we make. It's comfort care on dry skin, not a treatment for eczema, and the fuller buyer's version of that decision is in where tallow fits for eczema-prone skin. Sixty days on your skin; if it disagrees, we refund it.
Questions we hear
Can nickel actually cause eczema?
Nickel is the leading cause of contact dermatitis, so it definitely causes one kind of eczema on the skin it touches. The systemic version, where eating nickel worsens eczema elsewhere, is real but narrower: it applies to people already shown to be sensitized, and it's confirmed by oral challenge rather than by symptoms alone.
Should I try a low-nickel diet?
Only with a clinician, and ideally after testing. The dermatology review is explicit that it produces fewer and milder flare-ups in nickel-sensitive patients rather than clearing dermatitis, and it's written for diagnosed patients. Cutting whole grains, legumes, nuts and cocoa is a real nutritional change to make on a hunch.
Does histidine work for eczema?
One pilot suggests something. Twenty-one adults completing a crossover trial of 4 g a day showed SCORAD down 34% and 32% and POEM down 39%, with no placebo benefit, and the authors name the sample size as the limitation. Promising nutrition research, not an established treatment, and not a dose I'd hand anyone.
Will zinc help my body clear nickel?
Zinc induces metallothionein, which is well established, and metallothionein handles zinc and copper. The jump from there to eating zinc so your body releases nickel is her framework rather than something the metallothionein literature shows. Zinc deficiency does affect skin, and the adult upper limit is 40 mg a day.
Is tallow good for eczema-prone skin?
It's an emollient, and emollients are standard supportive care between flares. A plain fat with no fragrance and no preservatives gives reactive skin fewer things to react to, which is the whole argument for it. It isn't a treatment, and on broken or weeping skin nothing goes on without a clinician's say-so.
What about my dental work?
Worth asking your dentist about, and worth nothing more than the question. Fixed appliances measurably raise salivary nickel early in treatment, nickel-lean materials exist, and your dentist knows what's in your mouth. The rule there is the same as here: questions for a dentist, never decisions made alone.
Go deeper
The mechanism half of this lives in barrier repair 101 and the dental half in the mouth as skin upstream. The series hub is Skin Terrain 101, and the orientation piece is skin is downstream. For the itch-and-immune side there's mast cells and histamine, and for scale-prone skin, tallow for psoriasis-prone skin. On the product side: where tallow fits for eczema-prone skin, the shortest-label jar for sensitive skin and the pillar, the beef tallow for skin guide.
Sources
- Andra Sitoianu, The Bioavailable Naturopath (2025). Heavy Metals, Filaggrins, and Eczema. Substack. The thesis is in the subtitle; the article itself is behind her paywall and is not reconstructed here.
- Andra Sitoianu, The Bioavailable Naturopath (2025). From Mouth to Microbiome: How Nickel Can Trigger IBS and IBD Flares. Substack. Free in full, and the source of her exposure framing and food lists.
- Andra Sitoianu, The Bioavailable Naturopath (2025). Nickel Detox: The Method Behind My Approach. Substack. Free preview only; her metallothionein framing and mineral-balancing tradition come from the visible portion.
- Andra Sitoianu, The Bioavailable Naturopath. X thread on filaggrin and L-histidine, December 27, 2024, also unrolled at Thread Reader, and her X reply on severe eczema naming histidine, zinc, vitamin D3, a low-nickel diet and fungal testing.
- Braga M, Quecchia C, Perotta C et al. (2013). Systemic Nickel Allergy Syndrome: Nosologic Framework and Usefulness of Diet Regimen for Diagnosis. International Journal of Immunopathology and Pharmacology 26:707.
- Ricciardi L, Arena A, Arena E et al. (2014). Systemic Nickel Allergy Syndrome: Epidemiological Data from Four Italian Allergy Units. International Journal of Immunopathology and Pharmacology 27:131.
- Sharma AD (2013). Low Nickel Diet in Dermatology. Indian Journal of Dermatology 58:240.
- Tan SP, Brown SB, Griffiths CEM, Weller RB, Gibbs NK (2017). Feeding filaggrin: effects of l-histidine supplementation in atopic dermatitis. Clinical Cosmetic and Investigational Dermatology 10:403.
- National Institutes of Health Office of Dietary Supplements (2026). Zinc: Fact Sheet for Health Professionals. NIH ODS. With Krezel A, Maret W (2017). The Functions of Metamorphic Metallothioneins in Zinc and Copper Metabolism. International Journal of Molecular Sciences 18:1237.
- Hattangdi-Haridas SR, Lanham-New SA, Wong WHS, Ho MHK, Darling AL (2019). Vitamin D Deficiency and Effects of Vitamin D Supplementation on Disease Severity in Patients with Atopic Dermatitis. Nutrients 11:1854.
Brian is the founder of Craft Tallow, a small-batch tallow skincare line shipped from Cottonwood Heights, Utah, built on 100% grass-fed suet. Questions? Reply to any email from us; it lands with him.