Can we talk about all of the misleading information online about hair loss? One of the most common beliefs is that “hard water causes hair loss.” Now, there are some studies that support the idea of hard water causing hair breakage, but there are also studies that say it has no definitive impact on hair.

From this, we can conclude that hard water may not necessarily correlate with hair breakage for everyone. But, before we get into the details about this, let's talk about what hard water actually is and the difference between hair loss versus hair breakage.

What is hard water?

“Water hardness” is the amount of dissolved calcium and magnesium in the water. Hard water is high in dissolved minerals, mainly calcium and magnesium. It is commonly believed that the usage of hard water results in hair breakage.

What is hair breakage?

Firstly, hair loss is when hair falls out from the scalp or “hair follicle,” and this is called alopecia. There are different types of alopecia, and hard water cannot cause alopecia or “hair loss from the scalp.”

Hair breakage is when the hair breaks off from the shaft. Hair dryness, heat treatments, tension, and split ends are the most common causes of hair breakage. But, at the same time, there is research to support the belief that hard water can have some effect on the skin and likewise the scalp.  

Does hard water cause dry skin?

When it comes to hard water, the most associated effect is dryness and irritation. There have been more studies on the occurrence of hard water causing dry skin than hair breakage. “A 2018 case–control study of 80 young adults with a mean age of 26 years showed that skin sites washed with hard water significantly increased sodium lauryl sulfate (SLS) deposits, which in turn increased "transepidermal water loss" (dryness) and caused skin irritation.“ 

“This is due to the water’s inability to properly dissolve soaps (both used directly on the skin and detergents used on laundry). The unrinsed soap draws out the skin’s natural oils, and causes the skin to be dry, flaky, and itchy.”

However, this is not to say that mineral build-ups from hard water cause dry skin for everyone. Most of these instances are shown in people with eczema. In fact, there is a 2022 study with “findings that suggest that higher domestic hard water concentration exposure was associated with an increase in odds of atopic dermatitis, a type of eczema, in middle‐aged adults.”

“Eczema (atopic dermatitis) is a chronic inflammatory skin disease characterized by compromised skin barrier function. Eczema is caused by the interaction of genetics, the immune system, and environmental factors.“

So, while hard water cannot cause atopic dermatitis, there is evidence to suggest that it can increase the odds of it flaring up because of its lessened ability to wash away drying ingredients such as SLS. 

It’s also true that the minerals within hard water can lower the pH of water. Therefore, it can affect how the skin barrier works. Moreover, the calcium and magnesium ions within hard water bind to specific soap particles called surfactants.

This binding makes soap harder to rinse away, and this is what’s known as “soap scum.” According to the Journal of Investigative Dermatology, when soap scum is left on the skin, it can exacerbate conditions such as atopic dermatitis and seborrheic dermatitis. 

Seborrheic dermatitis  mainly affects the scalp, and it presents with dryness and dandruff. As a result, some studies suggest that hard water may worsen seborrheic dermatitis.

This dryness can damage the skin barrier and irritate the skin. And yes, when the scalp is dry, the hair shaft is often dry. Thus, this dynamic can lead to hair breakage. However, hard water will not have this effect on everyone. To be even more specific, it will not even have this effect on the majority of people. So, it’s contentious to say that “hard water” causes hair breakage.

Regarding actual hair loss – in severe cases of eczema, which could hypothetically be exacerbated by hard water, you might scratch your scalp so much that you damage the hair follicles. In turn, this might cause hair loss. But, this is not truly “the result of hard water.”

To combat the potential effects of hard water, you can purchase a shower head filter, a shampoo without sulfates, and you can also purchase a hydrating shampoo for sensitive skin. Additionally, it’s important to use lukewarm water and to use a nourishing conditioner.

Sources:

https://www.manhattanbeach.gov/departments/public-works/utilities-division/water-systems/treatment/hard-facts-about-hard-water

https://www.medicalnewstoday.com/articles/325026

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3927171/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9804584/#:~:text=Our%20findings%20suggest%20that%20exposure,reducing%20eczema%20prevalence%20in%20adults.

https://scholar.google.com/scholar_lookup?journal=J+Invest+Dermatol&title=The+effect+of+water+hardness+on+surfactant+deposition+after+washing+and+subsequent+skin+irritation+in+atopic+dermatitis+patients+and+healthy+control+subjects&volume=138&publication_year=2018&pages=68-77&pmid=28927888&

https://www.healthline.com/health/eczema/hard-water-and-eczema#research

https://www.ajmc.com/view/atopic-eczema-significantly-associated-with-excessive-scarring-in-new-uk-analysis

https://www.healthline.com/health/hard-water-hair-damage-treatment