Why are more and more people experiencing hair loss?

It's a question many ask, especially when, despite using good products, hair seems to "fall out more than usual." The answer isn't always in shampoos or treatments, but in something more invisible and constant: the type of water we bathe with.

It is estimated that 85% of the world's water supply that reaches homes contains a high concentration of minerals and some chemicals that turn it into hard water; and although it is safe for health, these minerals do have a significant physical effect on hair, altering its structure and strength.

What does science tell us about this?

In 2018, a study published in the International Journal of Trichology analyzed how hair strength changes after exposure to hard water. The results were clear: hair treated with hard water showed a significant decrease in tensile strength, meaning it became more fragile and easier to break.

Researchers measured the force each strand could withstand before breaking. The group washed with purified water maintained an average resistance of 255 units, while the group exposed to hard water dropped to 234 units, a statistically significant difference (p = 0.001). In simple terms: hard water reduces the natural strength of hair.

It does not weaken it from the root, as happens in cases of androgenic or areata alopecia, but it does increase loss due to breakage, which leads to more abundant shedding.

Why does this fragility occur?

Hard water elements adhere to the surface of the hair shaft and form microscopic mineral deposits. Over time, these residues alter the cuticle, which is the outer layer responsible for protecting and maintaining hair hydration. When the cuticle becomes irregular, the hair:

• loses flexibility,
• reflects less light,
• tangles easily,
• and breaks with less tension.
  
  

Visually, this translates into hair that is drier, frizzy, and lifeless; microscopically, into a weakened hair fiber that fragments before reaching its ideal length or thickness.

Does this mean hard water causes hair loss?

Yes, and no.

Hard water does not cause loss from the root or affect the follicle, so it is not related to hereditary or hormonal alopecia. What it does produce is mechanical loss: hairs break at different lengths, which ultimately leads to less density and the sensation that hair is not growing.

This difference between shedding and breakage is key to understanding why many people who do not have hair health problems lose hair when brushing or washing. In most cases, it is not follicular loss, but breakage due to weakening of the hair fiber.

Can hard water affect other aspects of hair care?

Absolutely. The same mineral deposits that weaken hair also interfere with the effectiveness of hair products. Shampoo lathers less, conditioner doesn't penetrate, and moisturizing or restorative treatments don't work with the same depth.

Over time, this leads to a buildup of residue that intensifies the feeling of heaviness and dryness, making it a vicious cycle. Hard water is an aesthetic and structural factor that affects hair at a microscopic level. Minerals are not seen or felt immediately, but their cumulative effect translates into more fragile, duller hair fiber with a greater tendency to break.

Understanding this relationship between water and hair is fundamental to understanding that not all hair damage comes from products or heat: sometimes, the cause is the water itself.