Why silver is in there
Silver is an antimicrobial: it kills bacteria. In period underwear that is used for odor control, because the smell associated with menstrual blood comes from bacteria acting on it. So a silver-treated pair is, in effect, marketed as a fresher-smelling pair. That is the upside the brands are selling.
The concern, and its limits
The worry is that the vagina depends on beneficial bacteria (lactobacilli) to stay healthy, and an antimicrobial that kills bacteria indiscriminately might not distinguish the bad from the good. A 2018 lab study (Tian et al., ACS Applied Materials & Interfaces) found that silver nanoparticles killed two beneficial Lactobacillus species, L. delbrueckii subsp. bulgaricus and L. casei, in a dish, while two common pathogens survived. Those are dairy and gut species, not the vaginal strains, and the study did not test underwear. The FDA says it is researching nanosilver in menstrual products and has published no finding. Consumer testing (by Which? and Altroconsumo) has found measurable silver in some period pants.
The limit on all of this: the direct effect of wearing silver-treated underwear on the vaginal microbiome has not been studied. So the concern is a reasonable caution built on a real lab finding and a plausible mechanism, not a proven harm. Anyone who states it as settled, in either direction, is going beyond the evidence.
The advocacy view, and how to avoid it
Advocacy groups such as Women's Voices for the Earth argue that antimicrobial treatment solves a problem that does not need solving - odor is manageable with normal washing - while adding uncertainty against sensitive tissue. Whether that persuades you is personal. If you would rather skip silver: check the product page and materials for "silver," "antimicrobial," or "odor-control technology," and choose untreated or cotton-topped styles instead. For odor, washing properly (rinse cold until it runs clear, no fabric softener) does the same job without the additive.
Sources
The claims above trace to:
- 2018 lab finding that silver nanoparticles kill beneficial lactobacilli: Tian X, Jiang X, Welch C, et al. "Bactericidal Effects of Silver Nanoparticles on Lactobacilli and the Underlying Mechanism." ACS Applied Materials & Interfaces, 2018;10(10):8443-8450, doi:10.1021/acsami.7b17274 (PubMed 29481051). Earlier versions of this page called it an FDA study, following an advocacy summary; it is not.
- Silver measured in some period pants: Which? and Altroconsumo consumer testing.
- That the direct effect on the vaginal microbiome is unstudied, and the advocacy critique: Women's Voices for the Earth / Weaving Voices.
Quick answers
- Is silver in period underwear safe?
- It is genuinely uncertain, and careful sources say so. Silver is antimicrobial, and a 2018 lab study (Tian et al.) found silver nanoparticles kill two beneficial Lactobacillus species in a dish, but those were not vaginal strains and the effect of actually wearing silver-treated underwear on the vaginal microbiome has not been directly studied. If that uncertainty bothers you, untreated or cotton-topped styles avoid it.
- Why do period underwear have silver in them?
- For odor control. Silver kills the bacteria that produce the smell associated with menstrual blood, so a silver-treated pair is marketed as staying fresher. The trade-off is the antimicrobial question - it kills bacteria without distinguishing the beneficial ones.
- How do I find period underwear without silver?
- Check the materials and product description for "silver," "antimicrobial," or "odor-control" language, and choose styles that do not list it - cotton-topped styles are a good bet. Proper washing controls odor without the additive.
Related guides
PFAS in period underwear: the lawsuits, the testing, and what it actually means
What PFAS "forever chemicals" are, the Thinx and Knix class-action settlements, the independent lab testing, and what was established and what was not.
Period underwear and yeast infections: breathability and vaginal health
Non-breathable synthetics trap heat and moisture, which can raise the risk of yeast infections for some people. How to lower it, without the alarmism.
Best cotton and organic period underwear
Period underwear with a cotton or organic-cotton top layer for sensitive skin, and what "cotton" means once there is an absorbent core under it.
Want the one-page version of the data behind these guides? The printable absorbency cheat-sheet puts every brand's tiers in millilitres on a single sheet - free, no email needed.
The whole safety picture
Silver is one additive; PFAS is the other. The safety hub pulls them together with the regulation gap and vaginal-health concerns, each with its sources.