Climate and relocation

Hard water and skin: what the research shows, and what renters can do

Climate and relocation · Published 2026-10-21

People who move to a new city often blame the water when their skin starts to itch or their hair feels different. Sometimes they are right. Water hardness varies enormously between regions, and there is a real body of research on how hard water interacts with soap and the skin barrier. There is also a lot of marketing for filters and softeners that the evidence does not fully support. Here is what is known.

What makes water "hard"

Rainwater is naturally soft. As it passes through limestone, chalk and other rocks, it picks up calcium and magnesium. Regions on chalk or limestone tend to have hard water; regions on granite or with water drawn from rain-fed reservoirs tend to have soft water. Your local water supplier usually publishes hardness figures, often in mg/L of calcium carbonate. The US Geological Survey, for example, classes water at 121 to 180 mg/L as hard and above 180 mg/L as very hard; classifications vary by country.

Signs at home include limescale on kettles and taps, soap that lathers poorly, and a film on glass shower screens.

What hard water does with soap

Calcium and magnesium ions bind to surfactants such as sodium lauryl sulfate (SLS), a common foaming agent, and make them less soluble, so more of them stay behind on the skin after rinsing. In a controlled study published in the Journal of Investigative Dermatology (Danby and colleagues, 2018), 80 volunteers, including people with atopic dermatitis, had skin washed with SLS in water of different hardness. Sites washed with hard water had significantly more SLS deposited, which increased water loss through the skin and irritation, particularly in people with eczema carrying a mutation in the filaggrin gene. Removing the calcium and magnesium by ion-exchange softening reduced the residue. Chlorine showed no clear effect. The study was partly funded by a water-softener company, which is worth knowing, but the design was controlled and the mechanism is plausible.

Hard water and eczema

• Infants: a study of 1,303 three-month-old infants in the UK (Perkin and colleagues, 2016) found that higher domestic water hardness was associated with a higher risk of eczema in early life.
• The overall picture: a 2021 systematic review and meta-analysis (Jabbar-Lopez and colleagues, Clinical & Experimental Allergy) pooled observational data on more than 385,000 participants and found increased odds of eczema in children exposed to harder water (odds ratio about 1.28), with very low certainty of evidence.
• Treatment: the same review found that two randomized trials of water softeners did not show a significant improvement in objective eczema severity in people who already had eczema.
• Prevention: a pilot trial (SOFTER, 2022) installed softeners before birth in hard-water homes in London. It showed that a full trial is feasible; it was not designed to prove an effect. Notably, 28% of eligible families could not have a softener installed, for technical reasons or because the landlord did not approve.

And hair?

Results are mixed. A small study (Srinivasan and colleagues, 2013) found no difference in hair strength or elasticity after 30 days of soaking in hard versus distilled water; a later study (Luqman and colleagues, 2018) reported lower strength with hard water. Many people notice that hair feels coated or dull and tangles more in hard water, which conditioner helps with. Our guide to a honey leave-in conditioner explains how conditioning agents work.

After a move: how to check

1. Look up your water supplier's hardness figures for your area.
2. Look for limescale in the kettle and on taps after a few weeks.
3. Notice timing: does skin feel tight or itchy straight after showering, and better after a swim in a pool or after a trip?
4. Consider other changes at the same time: climate, indoor heating or air-conditioning, new products, stress. Our guide to moving to a new climate goes through them.

Chlorine and other differences

Tap water differs in more than hardness. Many supplies are disinfected with chlorine or chloramine, which some people find drying or irritating, although the Danby study found no clear effect of chlorine on skin irritation from soap. Water temperature and pressure also vary from home to home, and a powerful, hot shower is harder on the skin barrier than the water's mineral content. If your skin changes after a move, adjusting shower habits is often the easiest place to start.

What renters can do

Ion-exchange softeners are installed on the main supply and usually need the owner's permission. Without one, you can still limit the effect:

• Use gentle, low-foam cleansers, and less of them. Surfactants are what hard water leaves behind.
• Rinse thoroughly, a few seconds longer than feels necessary.
• Keep showers short and warm, not hot.
• Moisturize immediately after drying, while skin is damp.
• Be cautious about shower filters' claims. Many reduce chlorine or sediment; few soften water meaningfully. Check what a filter actually removes.
• For babies with eczema in the family, discuss washing routines with a doctor or health visitor.

Hard water is one part of a city's "skin environment" alongside humidity and air quality. See also pollution and skin.

Read next

More in Climate and relocation

Climate and relocation

Moving to a new climate: adapting your skincare

Humidity, UV, water and air change when you move. A climate-by-climate plan for the first months in a new city.

Climate and relocation

Pollution and skin

Fine particles, traffic soot, ozone and UV: what studies link to skin, and why 'anti-pollution' claims need care.

Climate and relocation

Gisou's honey leave-in, decoded

A honey-based leave-in read from its label, and how humectants behave in tropical humidity and dry air.