Every Tampon They Tested Had Heavy Metals. No One Could Tell Me About Nickel.

It was 5:40 in the morning and I was standing in a pharmacy aisle holding a box of organic tampons, having a thought I did not want to have.

I know too much about heavy metals to buy personal-care products without thinking about them. And I had just spent months reading a literature that keeps converging on an uncomfortable finding: "organic" does not mean "low in heavy metals," and for some elements it can mean the opposite. So I did the thing a normal person does not do at 5:40 a.m. I called the number on the box to ask whether they test for nickel.

The call would not go through.

I still do not have an answer. What I have instead is the data, and the data deserves your attention, because the odds are good you have never once thought about what is in the product you are putting inside your body for a quarter of your adult life.

Every tampon they tested contained metal

In 2024, a research team led by Jenni Shearston published the first peer-reviewed study to measure metals in tampons [1]. They tested 30 products across 14 brands for 16 metals, using inductively coupled plasma mass spectrometry, the same method I rely on in certification work. They found measurable concentrations of all sixteen, with lead, cadmium, and arsenic among the most prominent [1].

Tampons have been sold in the United States for more than ninety years. This was the first time anyone tested them for heavy metals.

Sit with that for a second.

Organic tampons carried the most arsenic

Here is the part that sent me to the phone. The study split the results by product type, and the pattern is not the one the marketing would predict. Lead ran higher in the non-organic tampons. Arsenic ran higher in the organic ones. Nickel showed up across both [1].

I wrote about this exact reflex in my paper on functional fiber: the health halo, the trained assumption that a "clean" label maps onto a clean product. Organic certification governs how a crop is grown. It says nothing about the metal content of the soil it is grown in, and organic cotton leans on natural soil amendments like manure and compost that are themselves vectors for arsenic. The certification was never designed to catch this, so it does not. The word on the box that you were taught to trust is the word that tells you the least about the question I was asking.

The metal I was calling about

Most of the coverage of that study fixed on lead and arsenic, because those are the metals that frighten people. I was calling about nickel, and I want to explain why, because it sits at the center of my work.

Diseases have microbiome signatures. They also have metallomic signatures, the specific pattern of metals that accumulates in a tissue or a person. The spine of microbial metallomics, the framework I have spent years building, is that these two are linked. The metallomic signature acts as a selective pressure on the microbiome, and the microbiome it selects for drives pathogenesis. Metals reshape microbial communities by altering local pH and generating oxidative stress, suppressing some taxa and selecting for metal-tolerant ones [9], and in humans, measured metal exposure tracks with measurable shifts in microbiome composition [10].

Endometriosis is where this gets specific. Women with endometriosis carry distinct alterations in their gut and reproductive-tract microbiomes [8, 11]. They also carry elevated nickel: one case-control study found whole-blood nickel more than three times higher in women with endometriosis than in controls [6]. And when you take dietary nickel away, symptoms improve. In an open-label study, 90.3% of endometriosis patients with treatment-resistant gut symptoms tested positive for nickel sensitivity, and after three months on a low-nickel diet their gastrointestinal, systemic, and pelvic-pain symptoms fell significantly [4]. A 2022 systematic review pointed the same way: a low-nickel diet may reduce endometriosis pain [5]. The mechanism is allergic contact mucositis, a local immune reaction to dietary nickel that drives systemic inflammation, and it is common, with a prevalence above 30% in the general population [7].

I will be precise about what that does and does not mean, because precision is the whole point. A low-nickel diet helps the subset of women whose disease is aggravated by nickel sensitivity, and the evidence so far comes from small, mostly uncontrolled studies [4, 5]. It is not a cure for endometriosis. The blood-nickel association is correlational [6]. For a meaningful number of women, nickel makes the disease worse, and we have a tool that helps. I am not claiming nickel causes endometriosis.

Now hold that next to a product that sits, for hours at a time, against one of the most absorptive surfaces in the body, and that contains nickel no one is measuring for you. I have written before about nickel as a catalytic driver of disease. This is the same metal, arriving by a route nobody is watching.

Does it actually get into you? The honest answer.

This is where I have to be as careful with my own argument as I am with everyone else's. The Shearston study measured how much metal is in a tampon. It did not measure how much gets out of one and into you [1]. Those are different questions, and the second is the one that matters.

The early answers are partly reassuring, and I will give them to you straight. After the study, the FDA ran its own bench analysis and concluded that the metals it measured carried margins of safety indicating negligible toxicological concern under expected use [2]. A separate modeling study of lead found that under realistic wear, less than 0.3% of the lead theoretically released would be available to cross vaginal tissue, with most of it reabsorbed back into the tampon [3]. If your fear is that your tampons are acutely poisoning you, the current evidence does not support that fear, and I would rather tell you so than frighten you into a panic I cannot justify.

Read what those studies actually covered, though. They modeled lead. They tested under standardized conditions. Not one of them answered my question, which was about nickel, in my product, at the dose I would absorb. The vaginal epithelium is genuinely more permeable than skin, which is precisely why it is used to deliver drugs into the bloodstream. "Probably fine for lead" is a narrow claim. It does not clear nickel, and nobody has tried to.

The actual problem is that no one will tell you

Here is what genuinely unsettled me in that aisle: the realization that I could not get an answer.

Tampons are regulated as medical devices, which means the representatives answering the customer line are not equipped to discuss ICP-MS data, and there is no requirement that a manufacturer disclose the heavy-metal content of the product at all. So a reasonably informed person, standing in a pharmacy before dawn with a specific question about a specific metal, has no way to get one. The call does not go through. There is no panel to read. The "organic" on the box is the cue that tells you the least about what you are actually asking.

This is the exact gap my work exists to close. The Heavy Metal Index exists so that the evidence on a contaminant is traceable to its source instead of locked inside a lab report you will never see. Heavy Metal Tested certification exists because "trust us" is not a testing protocol, and because personal-care products belong inside a heavy-metal standard rather than outside it. I built these because of mornings exactly like this one.

What you can actually do

• Stop reading "organic" as a metals claim. It governs farming practice, and it leaves contamination untouched [1].
• Favor products whose makers publish third-party, batch-level heavy-metal testing. A real certificate is worth more than a reassuring adjective.
• If you are managing nickel-driven symptoms, medical-grade silicone cups and discs sidestep the agricultural supply chain that carries these metals into cotton and rayon in the first place.
• Ask. Call the number, email the company, request the panel. The reason nobody tests for this is that nobody is demanding it, loudly, in numbers.

The point

I did not write this to tell you to throw out your tampons. The data does not justify panic, and I will not manufacture it.

I wrote it because of the distance between how confident we are that these products are fine and how little anyone has actually checked. Sixteen metals, in every tampon tested, the organic ones included, sitting against an absorptive surface for a quarter of a woman's adult life, with no one screening for the metal most tied to a disease that affects roughly one in ten women, and no way to get an answer when you call to ask.

You have probably never thought about this. Neither had anyone else, for ninety years. The question worth sitting with is whether you have any way of knowing what is in the product you trust, and who you would even ask. It is not whether your particular brand is dangerous.

So here is the only question that matters this morning: does your brand test for this?

For the framework behind the metallome-microbiome-disease argument, see Microbial Metallomics and the open encyclopedia at WikiBiome. For the endometriosis microbiome work specifically, see the triangulation-method case study and Microbiome Medicine.

References

1. Shearston, J. A., Upson, K., Gordon, M., Do, V., Balac, O., Nguyen, K., Yan, B., Kioumourtzoglou, M.-A., & Schilling, K. (2024). Tampons as a source of exposure to metal(loid)s. Environment International, 190, 108849. doi:10.1016/j.envint.2024.108849
2. Jin, Y., Eppihimer, M., Alam, M. S., Powell, A. T., Margerrison, E., & Nawaby, A. V. (2026). Do metals in tampons pose a health risk? A toxicological risk assessment study. Toxicological Sciences, 209(6). doi:10.1093/toxsci/kfag065
3. Ellison, C. A., Doyle, P. R., Haven, C. A., McClenathan, D. M., Obringer, C. M., & Woeller, K. E. (2026). Integrating experimental data and mechanistic modeling to assess potential lead exposure from tampon use. Toxicological Sciences, 209(5). doi:10.1093/toxsci/kfag052
4. Borghini, R., Porpora, M. G., Casale, R., Marino, M., Palmieri, E., Greco, N., Donato, G., & Picarelli, A. (2020). Irritable Bowel Syndrome-Like Disorders in Endometriosis: Prevalence of Nickel Sensitivity and Effects of a Low-Nickel Diet. An Open-Label Pilot Study. Nutrients, 12(2), 341. doi:10.3390/nu12020341
5. Sverrisdóttir, U. Á., Hansen, S., & Rudnicki, M. (2022). Impact of diet on pain perception in women with endometriosis: A systematic review. European Journal of Obstetrics & Gynecology and Reproductive Biology, 271, 245–249. doi:10.1016/j.ejogrb.2022.02.028
6. Silva, N., Senanayake, H., & Waduge, V. (2013). Elevated levels of whole blood nickel in a group of Sri Lankan women with endometriosis: a case control study. BMC Research Notes, 6, 13. doi:10.1186/1756-0500-6-13
7. Borghini, R., De Amicis, N., Bella, A., Greco, N., Donato, G., & Picarelli, A. (2020). Beneficial Effects of a Low-Nickel Diet on Relapsing IBS-Like and Extraintestinal Symptoms of Celiac Patients during a Proper Gluten-Free Diet. Nutrients, 12(8), 2277. doi:10.3390/nu12082277
8. Salliss, M. E., Farland, L. V., Mahnert, N. D., & Herbst-Kralovetz, M. M. (2022). The role of gut and genital microbiota and the estrobolome in endometriosis, infertility and chronic pelvic pain. Human Reproduction Update, 28(1), 92–131. doi:10.1093/humupd/dmab035
9. Duan, H., Yu, L., Tian, F., Zhai, Q., Fan, L., & Chen, W. (2020). Gut microbiota: A target for heavy metal toxicity and a probiotic protective strategy. Science of the Total Environment, 742, 140429. doi:10.1016/j.scitotenv.2020.140429
10. Laue, H. E., Moroishi, Y., Jackson, B. P., Palys, T. J., Madan, J. C., & Karagas, M. R. (2020). Nutrient-toxic element mixtures and the early postnatal gut microbiome in a United States longitudinal birth cohort. Environment International, 138, 105613. doi:10.1016/j.envint.2020.105613
11. Uzuner, C., Mak, J., El-Assaad, F., & Condous, G. (2023). The bidirectional relationship between endometriosis and microbiome. Frontiers in Endocrinology, 14, 1110824. doi:10.3389/fendo.2023.1110824