Written by: Rhonda Davis
We've all experienced this: you shampoo, rinse, repeat and towel dry but somehow your hair still feels greasy, dull and slightly coated. Before you blame the shampoo, take a look at your tap. Hard water contains calcium and magnesium ions that react with the surfactants in your shampoo to form a residue, similar to the scummy ring you see around a bathtub. Some of that residue clings directly to your hair strands instead of rinsing away, leaving behind a film that feels a lot like grease.
And, yes there is a scientific reason why this happens.
This problem occurs in two ways. First, those mineral ions in your hard water react with the surfactants in your shampoo before the shampoo can even do its job of cleansing and removing the oil, dirt and grime from your hair. This reaction leaves more oil behind than intended. Second, our hair and skin have a negative charge, so if your conditioner uses positively-charged conditioning ingredients (which is very common for hair softness and detangling), hard water can change how those ingredients settle onto your hair. This is very similar to a magnet, where opposite ingredients attract to one another resulting in a film on the hair that feels greasy no matter how gentle or well-formulated the product actually is.
For those of you with soft tap water, you are in the clear and I love that for you.
For the rest of us who live in regions with notably hard water don't fret. The good news is this isn't a formula flaw you have to live with, it's simply a water chemistry issue with real fixes. Look for products that have chelating ingredients in the formula such as disodium or tetrasodium EDTA (the most common and found in our 2-in-1 Shampoo & Conditioner), sodium phytate (often paired with sodium gluconate), citric acid (also found in our 2-in-1 Shampoo & Conditioner), and etidronic acid, sometimes listed as HEDP. These chelating ingredients bind to calcium and magnesium so they can rinse away instead of bonding to your hair. If you'd like to truly combat hard water, you can also invest in a water softener but if that is not an option, an ion-exchange attachment such as a ShowerStick or a standard filtered shower head will also work.
Sources
- Effects of Hard Water on Hair — International Journal of Trichology, 2013 (via PMC/NIH)
- Scanning Electron Microscopy of Hair Treated in Hard Water — PubMed
- Scanning Electron Microscopy Study of Hair Shaft Changes Related to Hardness of Water — Indian Journal of Dermatology, Venereology and Leprology
- The Structural Implications of Water Hardness Metal Uptake by Human Hair — ResearchGate
- Hair Invisible Damages — Juniper Online Journal of Dermatology & Cosmetics