You’ve probably seen ads for Instagram-sleek shower filters that claim to make your hair and skin look and feel better.They warn of chemicals and contaminants in water, including chlorine, lead, microbes, and pesticides.And they promise to deliver a slew of benefits, such as soothing dry, itchy skin and reducing dandruff and eczema (AquaBliss); reducing acne and protecting the skin barrier (Filterbaby); hydrating skin and prolonging chemical hair treatments (Canopy); and providing “fewer psoriasis flare-ups,” “reduced hair shedding,” and even “enhanced overall wellbeing” (Jolie).Since some of the hardware costs more than $150 (not counting filter replacements), it’s reasonable to ask whether there’s any proof that these showerheads can deliver on their promises.