Hard Water and Your Hair

How Minerals, pH, and Water Quality Change Hair and Scalp Over Time

If your hair feels dull, rough, or coated no matter how carefully you choose your products, the problem may not be your shampoo—it may be your water. Hard water is common in both municipal systems and well water, and its effects build gradually with every wash.

At Mijo®, we consider water quality one of the key external factors shaping long-term hair and scalp health, alongside nutrition, hormones, and stress. It’s an everyday exposure that often goes unnoticed, yet it can subtly change how hair looks, feels, and behaves over time.

What Makes Water “Hard”?

Water is considered hard when it contains elevated levels of dissolved minerals, primarily calcium and magnesium. These minerals are usually measured as calcium carbonate (CaCO₃), and in many regions water falls into the moderately hard to very hard range—levels high enough to leave scale on plumbing fixtures and residue on hair [1,2].

What makes hard water especially challenging is that its effects are cumulative. Each wash leaves behind microscopic mineral deposits that slowly build up, altering hair texture, reducing shine, and making products feel less effective [2,3].

How Hard Water Interacts With Hair

Hair keratin carries a slight negative charge at the pH of most shampoos. Positively charged calcium and magnesium ions are attracted to the hair surface, binding to the cuticle and gradually working into its outer layers [3,4].

As these minerals accumulate, the cuticle can no longer lie flat. When cuticles stay slightly lifted, hair reflects less light and feels rougher. Friction increases, leading to more tangling and greater mechanical stress during brushing and styling—factors that contribute to breakage over time [4,5].

Effects on Hair Strength

Hard water doesn’t just affect appearance. Laboratory studies show that repeated washing in very hard water can reduce hair’s tensile strength, making fibers more prone to breakage compared with hair washed in deionized water [2].

While extremely hard water shows the most dramatic effects, even moderate hardness can contribute to slow, progressive weakening with repeated exposure. Mineral deposits may also promote oxidative reactions at the cuticle surface, similar to what occurs when metals are present during oxidative hair coloring, further stressing the hair fiber [3,5].

Hard Water and the Scalp

The scalp is living skin with its own barrier, microbiome, and ideal pH range. Hard water can interfere with all three. Mineral-rich water reduces the effectiveness of surfactants, making it harder to fully remove sebum, sweat, pollution, and styling residue [6].

Dermatology research shows that washing with hard water can raise skin surface pH and weaken the outer barrier layer, increasing transepidermal water loss and irritation—particularly in sensitive or compromised skin [7,8]. On the scalp, this disruption may show up as tightness, itch, flaking, or increased reactivity. Chlorine, commonly present in treated water, adds additional oxidative stress to the skin barrier [3].

Why Chelation and pH Matter

To remove mineral buildup, shampoos need chelators—ingredients that bind metal ions and keep them soluble so they rinse away instead of redepositing. Traditional chelators like EDTA are effective but environmentally persistent [9]. Modern cosmetic chemistry increasingly favors biodegradable alternatives that still bind calcium, magnesium, iron, and other metals effectively [10].

Chelation works best when paired with thoughtful pH control. At a mildly acidic pH (around 4.5–5.5), hair cuticles lie flatter and carry fewer negative charges, reducing further mineral attraction and supporting smoother, more resilient hair [11,12]. This same pH range supports scalp barrier enzymes and overall comfort [12,13].

The Mijo® Approach to Hard Water

At Mijo®, hard water is treated as a real, everyday disruptor of the scalp ecosystem—not a minor inconvenience. Our formulas are designed to manage mineral exposure while protecting the skin barrier, rather than chasing a stripped or "squeaky-clean" feel.

Mijo® shampoos rely on gentle, biodegradable surfactants, slightly acidic pH guided by lactic acid, and modern chelation strategies centered on Trisodium Ethylenediamine Disuccinate (EDDS). EDDS is a biodegradable chelator that effectively binds calcium, magnesium, iron, and other metals while offering a more environmentally responsible alternative to traditional EDTA [10].

Used within a carefully pH-adjusted system, EDDS helps lift mineral deposits from hair and scalp without over-stripping natural lipids or disrupting barrier proteins—an important distinction for sensitive, reactive, or aging scalps.

Why This Matters

Hair and scalp health sit at the intersection of many systems. Water quality, skin biology,and daily care choices all play a role. By pairing gentle cleansing, thoughtful pH control, and biodegradable chelation, Mijo® works with those systems to support both immediate comfort and long-term hair resilience—even if hard water is part of your daily life.

Because beautiful hair isn’t just clean—it’s informed.

References

1. Srinivasan G, Srinivas CR. Scanning electron microscopy of hair treated in hard water. Int J Trichology.2015;7(3):123–127.

2. Luqman MW, et al. Changes in baseline strength of hair treated with deionized and hard water. J Pak Med Assoc.2018;68(7):1035–1038.

3. Evans TA, Wickett RR, Kempka KJ. Structural implications of water hardness metal uptake by human hair. Int J Cosmet Sci. 2012;34(1):1–9.

4. Alibrahim EA, et al. Hair shaft changes related to water hardness. Indian J Dermatol Venereol Leprol.2018;84(3):337–341.

5. Robbins CR. Chemical and Physical Behavior of Human Hair. 5th ed. Springer; 2012.

6. Gavazzoni Dias MFR. Hair cosmetics: An overview. Int J Trichology. 2015;7(1):2–15.

7. Ananthapadmanabhan KP, et al. Cleansing without compromise. Dermatol Ther. 2004;17(Suppl 1):16–25.

8. Danby SG, et al. Effect of water hardness on surfactant deposition and skin irritation. J Invest Dermatol.2018;138(1):68–77.

9. Cosmetic Ingredient Review Expert Panel. Safety assessment of EDTA compounds. Int J Toxicol. 2002;21(Suppl 2):95–142.

10. Schowanek D, et al. Biodegradation of EDDS. Chemosphere. 1997;34(11):2375–2391.

11. Gavazzoni Dias MFR, et al. The shampoo pH can affect the hair. Int J Trichology. 2014;6(3):95–99.

12. Schmid-Wendtner MH, Korting HC. Skin surface pH and barrier function. Skin Pharmacol Physiol.2006;19(6):296–302.

13. Ali SM, Yosipovitch G. Skin pH: From basic science to basic skin care. Acta Derm Venereol. 2013;93(3):261–267.