Shower Filters, Facts and Fiction: Part 1

 Where to start. There is so much mixed-up information about shower filters out there. Which isn't helped by the fact that some brands make claims they cannot possibly achieve - but they still help even though they don't claim to do what they claim to do. ©Science-y Hair Blog 2024

Most filter claims are all about hard water, purifying water, or softening it. 

Softening water - a visual summary

Only a water softener you add salt to can actually soften water. "Soften" has a fixed definition in water-treatment, and also a less-clear one that is used in marketing.

- True water softening: A cation-exchange resin pulls out hard-water minerals (the cations, right!? Mostly Calcium and Magnesium) and trades them for salt. Softened water tends to feel a little slippery, whereas naturally soft water may not. A water softener is usually a large-ish appliance that softens all or most of the water for your entire home. There is only one brand of in-shower softener (Showerstick by Watersticks) and yes, you have to add salt to it - weekly for most homes.

- Pseudo-softening: Many shower filters claim to soften water. They aren't sticking to the water-treatment definition. They're making up their own. Maybe it removes chlorine, sediment, many can do that quite well. But to change actual hardness minerals? Nope. Maybe it claims to make your shower more alkaline with ceramic balls! You know how bleach solution feels slippery?  Baking soda dissolved in water feels a little slippery too. It's the alkaline quality that does that - and for a reason that has nothing to do with removing hard-water-minerals. Slippery and soft are not the same. Alkaline solutions react with the oils on your skin - breaking them down - it feels slippery.

There is so much to unpack here. I'm giving a green light (💚) to the things that filters CAN DO that are great for your hair. And rolling my eyes at the dodgier claims (🙄). 

• 💚 Removing or reducing chlorine disinfectant.  This is great for your skin and hair. Even if you don't have hard water, if you have city water, you have chlorine disinfectant. That can be drying and somewhat damaging to hair and can irritate skin. 
• 💚 Preserving hair color. This can result from reducing chlorine. More about that below.

• 🙄 Create alkaline shower water. Or "increase shower pH." Or "balance shower pH." Maybe that will make the water feel more slippery. Maybe that feels "softer?" There really isn't any good data supporting a higher pH as being better for skin or hair. Skin's natural pH is on the acidic side, and hair is at its most resilient at a pH that is around 6 (I have a wading-into-the-weeds post about that here). Tap water's pH can be all over the place - check with your water-treatment facility to find yours. 
• 🙄 Balance water pH? How can an in-the-box filter "know:" 1) The starting pH of the water. 2) What the end-goal is? 3) How to adjust for that? 
• If your water has a lower pH, it's possible that raising it with a shower filter might change the way products feel in your hair. But see the previous bullet point.

Why is hard water drying to skin and hair? I have a post about how minerals (hardness) deposit both IN and ON your hair here. That can cause a stiff or rough feeling, inflexibility, and dull appearance. Hard water minerals increase skin pH because they are alkaline when in solution. It takes skin hours to recover from that. Hair cannot adjust its pH - and while hair behaves differently than skin, those minerals are rather like having tiny amounts of gritty road dust in your hair....Things we call "dryness."  ©Science-y Hair Blog 2024

Hard water also interacts with many detergents, making them more difficult to rinse off. This is dehydrating to hair because those same detergents penetrate into hair and remove the protective oils and proteins under the cuticles. It's worse for sensitive skin, because that can cause prolonged trans-epidermal water loss. Which basically means your skin is can't retain water and - if skin were a plant - would be rapidly wilting. Instead - it gets dry and itchy and can become inflamed in sensitive individuals. ©Science-y Hair Blog 2024

Is chlorine damaging to hair? Repeated chlorine exposure in swimmers (which is more-concentrated and longer-duration than showering) show us that chlorine in water, which can and does get deep inside hair, damages hair proteins on the inside, damages cuticles (also made from protein) on the outside, degrades and removed oils on the surface of hair (and by extension in the cuticle layers), and strips color (natural pigments or dye).  ©Science-y Hair Blog 2024

In the shower - repeated exposure to chlorine in water is much lower than for the swimmers in the linked studies, but you can take away the idea that chlorine in tap water has damage-potential for hair. And if your hair is very tangle-prone or susceptible to breakage, or you frequently heat-style or highlight, color or otherwise chemically process your hair, chlorine might be more likely to make your hair feel less healthy.

Part 2 will cover types of shower filters, how to match that to your water situation, what you might not need, and some nagging about changing the filters as recommended. Because you might be able to save money on products by installing the right filter.

Part 3 has information about which filter media to choose, and a curated list of shower filters.

Science-y Hair Blog © 2024 by  Wendy M.S. is licensed under CC BY-NC-ND 4.0