Got hard water? Water that comes from limestone or sandstone aquifers in particular tends to contain minerals which cause it to be "hard." Primarily calcium and magnesium. These minerals interfere with many detergents, including soap. They can deposit on your skin, your shower, in plumbing.
People with itchy skin or eczema and dermatitis often try (or at least wonder about) water softeners to relieve their symptoms. First off, a shower-head water filter does nothing to remove minerals from water. These filters can remove chlorine and some "heavy" metals, but do not soften. That's another story.©Science-y Hair Blog 2013
A study in England tested 336 children, ages 6 to 16 years of age. All had eczema. All were treated for eczema with medication, but half were also given an ion-exchange water softener to test for 12 weeks.
Nurses evaluated the physical eczema symptoms and found no difference in measurable indicators of disease between the group which used softened water and the group with used their (hard) tap water. However on the more subjective (more difficult to measure accurately) aspects of the disease (itchiness, sleep loss), parents/children reported "small benefits." Even though these benefits could not be translated into measurable change in skin disease. Half of them decided to buy the water softener at the end of the study because they perceived a benefit. ©Science-y Hair Blog 2013
So the bigger the intervention, the bigger the perceived effect? Even when no difference could be measured? While a water softener might make a difference for some people; (and if so, how do we know whether it was the removal of minerals, or the addition of salt in their place?) soft water doesn't have enough support to be recommended by doctors. That's a good thing, because water softeners are expensive. I'd hate to invest in one and haul bags of salt every month and then have it make no difference! Not to mention they only last 8-10 years where I live.
©Science-y Hair Blog 2013
Placebo effect? Probably. I have a problem with how the study was designed.
Half the kids got a real water softener - then the other half should have had "sham" water softeners installed in their homes which did nothing. Just having the water softener and knowing it is going to alter your perception of your symptoms. Neither group should have known who had a real vs. the fake water softener, nor should the researchers have known.
To get really fancy, there are ways to record how many times a person wakes up to scratch, because loss of sleep is significant physical stress which can worsen eczema - but it is very difficult to guess just how much sleep you're losing, or how poor your sleep quality is because you wake up often.
Itchiness is very difficult to measure - that one will stay subjective.©Science-y Hair Blog 2013
Science can measure facts far more accurately than perceptions, and it's not only the job of scientists to be critical, but also the job of the public. By "critical" I don't mean, "complain about everything and be negative," I mean to wonder about what might have been studied differently. To wonder whether the assumed problem of minerals in the water is not a problem at all, but adding salt to water might make it less irritating to already itchy skin. To wonder whether people who thought they had a real water softener (but really had a fake one) might also report less itchiness (placebo effect). Placebos are not a bad thing - but it's better if they cost far less than water softeners.
That's it for now.
Source: Kim S. Thomas, Tara Dean, Caroline O'Leary, Tracey H. Sach, Karin Koller, Anthony Frost, Hywel C. Williams. A Randomised Controlled Trial of Ion-Exchange Water Softeners for the Treatment of Eczema in Children.PLoS Medicine, 2011; 8 (2)