The Himba Have Been Wearing Iron Oxide for Centuries

I have written a fair amount lately about traditional practices with no evidence behind them, and there is a version of that work which becomes tiresome and a little colonial — the visiting skeptic, arriving to inform people that their grandmother was wrong.

So here are three that hold up. Not folklore that happens to be charming. Instrument-measured, peer-reviewed, published data.

Otjize, and the iron oxide coincidence

Himba women in northern Namibia mix red ochre with butterfat and aromatic resin and wear it on skin and hair. It is the image everyone has seen. It is usually described in Western writing as ornamental or ceremonial, which it is, and as a sun and insect measure, which is how it is described by the women who wear it.

In 2022, researchers publishing in Scientific Reports put natural Namibian red ochre through high-resolution electron microscopy, X-ray diffraction and UV-visible spectroscopy.

What it is: predominantly nano-scale α-Fe₂O₃ — hematite — with some γ-FeOOH. Particle sizes around 17 to 31 nanometers on the basal dimension.

What it does: exceptional UV filtration with a sharp spectral cutoff near 570 nanometers, blocking over 97 percent of ultraviolet in the measured range, and reflecting at least half of incident solar heat in the infrared.

Read that cutoff figure again — 570 nanometers. Ultraviolet ends at 400. This material blocks UV and also a substantial chunk of visible light, into the green — precisely the wavelength range implicated in melanogenesis in richly pigmented skin.

Meanwhile, in the peer-reviewed dermatology of the last few years, the great discovery in photoprotection for skin of color has been that iron oxides are the ingredient that blocks visible light, that plain mineral sunscreen without them does not, and that tinted formulations are therefore not a cosmetic nicety but the functional product.

Nano-scale iron oxide, worn on the skin as a daily practice, in one of the highest-UV environments on earth, by a population with deeply pigmented skin. The authors do link the material’s properties to the low observed skin cancer rate in the community, and I want to be careful there — that is the authors’ proposed explanation, not an epidemiological study, and no such study of Himba skin cancer rates was located.

The materials chemistry is not in question. And the convergence is one of the more striking things I have come across this year: the formulation science arrived, several thousand years late, at an answer somebody was already wearing.

Argan oil, with a controlled trial behind it

Boucetta and colleagues, Clinical Interventions in Aging, 2015. Sixty postmenopausal women, randomized: thirty took 25 milliliters of dietary argan oil daily plus topical argan oil; thirty took dietary olive oil plus topical argan oil. Both arms received the topical, which isolates the dietary variable rather than the oil in general. Sixty days, with measurement by Cutometer and Reviscometer rather than by asking people how their skin felt.

Results in the argan-diet group: significant increases in gross elasticity, net elasticity and biological elasticity, all at p<0.001, and a decrease in resonance running time at p=0.002. Untreated control forearms showed no improvement.

This is one of the better pieces of evidence in this entire field — controlled, instrument-measured, with a design deliberately built to isolate one variable. Argan oil has been produced by Berber women’s cooperatives in Morocco for generations, and the trial is Moroccan.

Snail secretion filtrate, which has ten trials to its name

I resisted this one for a long time on aesthetic grounds and the literature does not care about my aesthetics.

A systematic review in the Journal of Integrative Dermatology identified ten clinical trials of snail-based products, including Lim 2020 (n=50), Addor 2019 (n=120, three arms), Draelos 2017 (n=40), Puaratanaarunkon 2022 (n=66), Fabi 2013 (n=25), Truchuelo 2020 (n=20, post-laser), Tribó-Boixareu 2009 (n=15) and Laneri 2019 (n=20).

Across those trials — and this is a systematic review rather than a meta-analysis, so these are individual endpoints reported side by side rather than a quantitative synthesis: significant reduction in transepidermal water loss against vehicle at p=0.026; 40 percent reduction in irregular pigmentation; 53 percent reduction in skin roughness at week twelve, p<0.001; a 31.40 percent decrease in inflammatory acne lesions with the active versus a 2.48 percent increase with placebo; periocular wrinkle improvement at p=0.03 at twelve weeks.

Ten trials with vehicle controls and instrument endpoints is a more serious evidence package than a great many things sold at four times the price with a clinical-sounding name. The Latin American folk product — baba de caracol — and the Korean cosmetic category converged on the same material from different directions, and the trials are mostly on standardized secretion filtrate rather than on the folk preparation, which is worth knowing before buying from a jar.

What I take from putting these three together

Not that tradition is validated, which would be its own kind of condescension — a practice does not need a trial to be worth keeping.

What strikes me is the direction of travel. Iron oxide was in the dermatology literature as a novel approach to visible-light photoprotection in about 2015, and on Himba skin for considerably longer. Argan had to wait for a Moroccan research group to run the trial on it. Snail mucin needed a Korean commercial category to acquire enough market value to be worth studying.

The evidence base is not a neutral record of what works. It is a record of what somebody decided to fund a study on, and that decision has always been made somewhere other than where the practice lives.

Which means the very long list of traditional preparations with no evidence behind them is telling you considerably less about those preparations than most people assume it is.

This article is educational and is not a substitute for care from someone who can look at your skin. Anything new, changing, painful or spreading should be assessed rather than researched.