A London-based underwear brand, Underdays, launched in 2021, is marketing underwear infused with probiotics and prebiotics, claiming it can benefit the vaginal microbiome and intimate health. The brand's UNDERskin™ knickers use a Swiss-developed technology called 'HeiQ Skin Care', which is designed to transfer beneficial bacteria and yeasts to the skin through continuous fabric contact.
The company states that the vaginal microbiome is an overlooked aspect of women's health, and their underwear aims to address issues arising from friction, heat, and sweat. The fabric also contains TENCEL fibers, intended to wick away moisture and inhibit bacterial growth, potentially reducing the risk of yeast infections. The technology is said to last up to 40 washes.
A month-long test of the probiotic underwear found them to be soft, comfortable, and discreet under clothing, with no reported negative side effects. However, the wearer did not note any significant positive changes.
Experts remain unconvinced about the efficacy of such products. Dr. Lamia Zafrani, a consultant gynecologist, stated that while good bacteria are crucial for vaginal health, underwear claiming to provide this externally lacks scientific validation. She suggests that consuming probiotics and prebiotics is a more beneficial approach. Similarly, consultant gynecologist Dr. Amit Shah noted a lack of high-quality clinical evidence supporting the idea that probiotic-infused underwear can alter the vaginal microbiome. He emphasized that the vagina possesses a robust natural ecosystem and recommended avoiding unnecessary products and harsh cleansers to support it.