No, it is not true that there are frequent travelers who will boil their underwear in hotel kettles. While some people may be tempted to use the kettle for this purpose, it is generally considered unhygienic and a health hazard.

While it sounds like an urban legend, there have been several viral social media posts and anecdotal reports from hotel housekeepers confirming that some guests do indeed use hotel kettles to "sanitize" their underwear or socks. The logic—however flawed—is that the boiling water will kill bacteria and freshen the garment when they run out of clean clothes. This practice is highly unsanitary and generally condemned by health experts and the hospitality industry. Kettles are designed solely for boiling water for consumption; putting fabric and human proteins into the vessel can lead to bacterial growth and persistent odors that the next guest will unknowingly encounter. Some travelers also reportedly use kettles to cook seafood or other odorous foods. Because of this risk, many seasoned travelers and "cleanliness influencers" advise either thoroughly rinsing a hotel kettle before use or avoiding it altogether, preferring to get their hot water from a coffee machine or the hotel's breakfast area instead.