Period pants marketed as eco-friendly alternatives to disposable menstrual products are being sold with undisclosed silver-based treatments that experts say may pose health risks and environmental harm. A new investigation by the UK consumer organization Which? tested leading brands and found notable silver concentrations in products from Bodyform, Marks & Spencer, Thinx, and Luna, despite the absence of legal limits or safety standards governing silver use in intimate apparel.

What Did the Testing Reveal About Silver in Period Pants?

Which? partnered with Italian consumer organization AltroConsumo to independently test a range of period pants brands for chemical contaminants. The results showed striking variation in silver content across products. Intima by Bodyform contained the highest levels at 126.7 milligrams per kilogram, while M&S period pants measured 57.8 milligrams per kilogram. Other brands showed lower concentrations: Thinx at 8.3 milligrams per kilogram, Luna at 7.4 milligrams per kilogram, and Modibodi at 0.9 milligrams per kilogram. Some brands, including Primark, Repeat, Wuka, Lovable, and Sloggi, had no detectable silver in the tests.

Reassuringly, the testing did not uncover per- and poly-fluoroalkyl substances, commonly known as PFAS or "forever chemicals," in any of the products tested. This finding is significant given that Thinx, a popular period pants brand, settled a class-action lawsuit in the United States earlier in 2026 after independent testing alleged the presence of both PFAS and nano silver in its products.

Why Are Manufacturers Adding Silver to Period Pants?

Brands add silver to period pants as an antimicrobial agent intended to combat odor and the spread of microorganisms. However, experts argue this addition is unnecessary and potentially problematic. There is no evidence that menstrual blood contains harmful bacteria requiring antimicrobial treatment, and normal hygiene practices are sufficient to keep period pants clean and fresh.

The irony is that silver treatments often don't even work as intended. When AltroConsumo tested 20 products containing silver for antibacterial purposes in 2013, only one-third of these products were actually effective at being antimicrobial. Many samples lost their silver content after just two washes, raising questions about whether the ingredient provides any real benefit.

What Health Concerns Do Experts Raise About Silver in Intimate Apparel?

Scientists have raised several concerns about silver-based treatments in products worn against sensitive skin. The types of silver used in textiles include nanosilver (microscopic particles), silver zeolite, silver copper zeolite, silver zinc zeolite, and silver chloride. These are distinct from inert silver used in jewelry and may behave differently in the body.

One major concern involves the potential for silver particles to migrate into the body and disrupt the skin microbiome by killing beneficial bacteria. The vulvar and vaginal tissues are especially absorbent and have unique properties that make them particularly vulnerable to exposure from textiles. A 2015 study conducted by the National Institutes for Food and Drug Control in Beijing found that nanosilver caused structural changes to vaginal mucosa, urethra, and rectum in rabbits, with the silver accumulating in the animals' blood circulation.

The U.S. Food and Drug Administration (FDA) has found that nanosilver can kill lactobacillus, the healthy bacteria in the vagina that help fight off infection. This disruption could increase the risk of bacterial vaginosis, sexually transmitted infections, and pregnancy complications. Additionally, the European Chemicals Agency (ECHA) states that silver zinc zeolite is suspected of having reproductive toxicity, though more research is needed.

"Manufacturers absolutely shouldn't be using silver nanoparticles in pants before a critical assessment of potential risks," said Thiago Verano-Braga, Associate Professor at Universidade Federal de Minas Gerais in Brazil, who has studied silver nanoparticles for years. "While the anti-microbial properties of silver nanoparticles have led to them becoming one of the most widely used nanomaterials in consumer products, there is a high chance of these nano particles being absorbed into the human body. Furthermore, it is important to test whether silver ions are being generated since they are extremely toxic and may be released from silver nanoparticles in acidic conditions. Typical vaginal pH is more acidic than neutral."

Thiago Verano-Braga, Associate Professor at Universidade Federal de Minas Gerais

What Are the Environmental Implications of Silver in Period Pants?

Beyond human health concerns, silver used in textiles can leach into waterways when period pants are washed, creating environmental contamination. This is particularly troubling given that many period pants brands market themselves as eco-friendly alternatives to disposable sanitary products. In the UK alone, 200,000 tonnes of disposable menstrual products end up in landfill each year, making the environmental argument for reusable period pants compelling. However, if those reusable products are treated with silver that contaminates water systems, the environmental benefit becomes questionable.

How to Choose Safer Period Pants?

• Check for Silver Disclosure: Review product packaging and manufacturer websites to see if silver-based antimicrobial treatments are mentioned. Many brands do not clearly disclose this ingredient, so contacting customer service directly may be necessary to get transparent information about what's in your pants.
• Prioritize Brands with No Detectable Silver: According to the Which? testing, brands including Primark, Repeat, Wuka, Lovable, and Sloggi showed no detectable silver in independent testing, though some of these brands may still use silver treatments not detected in this particular study.
• Follow Proper Care Instructions: Regardless of brand choice, washing and changing period pants according to manufacturer instructions is essential for hygiene. Normal, moderate hygiene routines are sufficient without relying on antimicrobial treatments to keep products safe and fresh.
• Request Transparency from Manufacturers: Consumer demand for clear labeling and disclosure of all antimicrobial treatments can push brands to be more transparent about what they're adding to intimate apparel and why.

Why Aren't There Legal Limits on Silver in Textiles?

Currently, there are no legal limits in the UK or most countries on how much silver can be added to period pants or textiles in general. The textile standard Oekotex, which certifies products for harmful substances, does not currently contain any requirements around silver content. This regulatory gap means manufacturers can use silver without restriction, even as scientific evidence raises questions about its safety in intimate products.

Legislation often lags behind new technology and consumer products. For context, period pants were only recently exempted from the "tampon tax," the value-added tax on sanitary products, in 2021. The slow pace of regulation means consumers may be exposed to substances that haven't been thoroughly evaluated for safety before legal frameworks catch up.

As period pants continue to grow in popularity as an eco-friendly alternative to disposable menstrual products, the absence of clear safety standards and transparent labeling leaves consumers without reliable information to make informed choices. The findings from Which? highlight the need for regulatory action to establish limits on silver and other antimicrobial agents in intimate apparel, as well as mandatory disclosure of these ingredients on product packaging.