Get the Facts: Hard Water

Get the Facts

By Suzanne Boothby

Published On: Aug 1, 2022

Last Updated On: Aug 5, 2022

Mineral deposits are a natural part of tap water – but what happens when the water from your faucet is full of extra minerals like calcium and magnesium? Research suggests that mineral-rich water, also known as “hard water,” can negatively impact eczema symptoms and introduce atopic skin conditions early in life.1

A 2020 review of 16 previous studies concluded that exposure to hard water could worsen symptoms of atopic dermatitis (AD) and may increase of the risk of eczema in young children. “Patients with eczema are much more sensitive to the effects of hard water than people with healthy skin,” said Dr. Simon Danby from the University of Sheffield’s department of infection, immunity and cardiovascular disease in a statement.2

Let’s explore the facts about hard water and review what you can do about it.

What is hard water and do you have it in your home?

The U.S Geological Survey (USGS) defines water hardness as the amount of dissolved calcium, magnesium and other minerals found in water.3 Water hardness can vary throughout the country, but areas in the West and Southwest, such as Las Vegas and Phoenix, are known for having it.4,5

If you’ve ever felt a slimy or chalky residue after washing your hands that might be a sign that you have hard water. Spots on your glasses after a round in the dishwasher can also be a clue. Hard water can also damage fabrics and clothing.

How does this residue get there? In general, our drinking water comes from two main sources: 1) surface water such as creeks, rivers and lakes; and 2) groundwater, found below the earth’s surface in cracks and spaces near soil, rock or sand. Water from both of source types must be treated before we drink or bathe in it, but the hard water comes from groundwater where the water interacts with rocks such as sandstone, granite and limestone picking up additional minerals. Want to check if your area has hard water? Try typing your zip code into this Water Hardness Map.6

There are also home water hardness tests available for purchase. Water hardness is commonly measured in milligrams per liter (mg/L) or parts per million (ppm). The U.S. Geological Survey offers general guidelines to help determine your water quality:

  • Soft water: 0-60 mg/L or ppm
  • Moderately hard water: 61-120 mg/L or ppm
  • Hard water: 121-180 mg/L or ppm
  • Very hard water: Over 180 mg/L or ppm.

If your home or work has hard water, could it be affecting your skin?

If you’re still reading and curious, you might have hard water in your home and you want to know what to do about it. Minerals found in hard water are not problematic to drink and are not known to cause any adverse health issues.8 However, they can accumulate on surfaces, leading to clogged pipes or damaged water heaters. Over time, topical exposure to hard water can also dry out your hair and harm your skin barrier. In fact, living in an area with hard water is associated with an increased risk of eczema, according to a study from researchers in London.9

“By damaging the skin barrier, washing with hard water may contribute to the development of eczema – a chronic skin condition characterized by an intensely itchy red rash,” said Danby, lead author of the study.

If hard water is affecting your eczema, this is how a water softener might help

If you are concerned about hard water, you may consider getting a water softener, which is similar to a water filter, as it works to remove any unwanted mineral compounds. Water treatment can improve hardness issues, according to the Water Quality Association,  a non-profit international trade association representing the water treatment industry.11

Pooled evidence from meta-analysis shows hard water likely negatively effects AD, but interventional studies thus far have not shown benefit overall. The effects of hard water seem most serious in conjunction with filaggrin mutation and disruptions in the skin barrier.12

A trial called the Softened Water for Eczema Prevention (SOFTER) is underway to investigate whether water softeners can help reduce the risk of eczema in babies.13 This study offers the first major look at the impact of using water softeners on babies in their own homes.

Other helpful water tips

Unsure about what’s in your water? The EPA requires community water systems to deliver an annual drinking water quality report (also known as a Consumer Confidence Report) to their customers each year in July. Educational info including the amount of minerals in your water should be in that report, along with contact information for your water provider. If you are having trouble finding information, you can call the EPA’s Safe Drinking Water hotline number: 1-800-426-4791. If you are one of the more than 15 million households who get their water from a private well, then you do not receive a water quality report, but you can visit the CDC’s Private Ground Water Wells page to get more info about testing your well.



Zarif K., et al. “The Effect of Water Hardness On Atopic Eczema, Skin Barrier Function: A Systematic Review, Meta-Analysis.” Clinical & Experimental Allergy, 1 December 2020.

[2] “The Hard Truth About Eczema: It’s Something in The Water.” The University of Sheffield Press Release, 21 September 2017.

[3] Water Science School. “Hardness of Water” USGS website, 11 June 2018.

[4] “Water quality FAQs” Las Vegas Valley Water District website.

[5] “2021 Water Quality Report.” City of Phoenix.

[6] “Water Hardness Map.” HydroFLOW USA website.

[7] Water Science School. “Hardness of Water” USGS website, 11 June 2018.

[8] “Water Softening.” PennState Extension Website, 11 July 2012.

[9] Danby, S, et al. “The Effect of Water Hardness on Surfactant Deposition after Washing and Subsequent Skin Irritation in Atopic Dermatitis Patients and Healthy Control Subjects,” Journal of Investigative Dermatology, January 2018.

[10] “Scale Deposits,” Water Quality Association website.

[11] “Water Softening.” PennState Extension Website, 11 July 2012.


[13] Warren R. Heymann, MD. “Striving For Hard Facts About Water Softening In Atopic Dermatitis.” Dermatology World Insights and Inquiries, 18 August 2021.

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