However, new research shows silver particles may kill off beneficial bacteria while leaving more resilient infectious bugs unharmed - leading to increased risk of bacterial infections. Of particular concern to experts are silver-containing period pants, marketed as an alternative to sanitary pads and tampons. There are no legal limits in the UK about how much silver can be added to period pants. A spokeswoman for M&S told Good Health that the company’s period-pant products still contain the same amount of silver as in the 2023 tests. Silver-containing period pants are also still sold by other major brands such as Victoria’s Secret and Next.