Image zoom Credit: Getty Images. A 2018 study found that bath toys, no matter how much soap they splash in each night, are quite susceptible to "the proliferation of opportunistic pathogens and unwanted organisms." Yes, organisms. Indeed, the same research found that every bath toy studied tested positive for the presence of mold and other "biofilms", including (gag) fecal matter. Just about any tub toy can become a breeding ground for mold and mildew simply due to the nature of its use. Think about it: the toy soaks in warm water for several minutes, each day or every other day. Then, it sits around in a warm, humid bathroom without being dried off (thanks to the diaperless toddler who promptly went running down the hall post-bath) and possibly even with standing water inside it. It's an invitation for a host of germs. So are they harmful?