Nobody Told Me That What Came Out of My Tap Could Be Making My Baby’s Skin Worse

This article is part of the Nella Vosk Complete Guide to Baby Eczema for Australian Families — everything you need to know about managing eczema-prone skin from the early months through toddlerhood.

This article is part of Nella Vosk’s Nobody Told Me series — a growing collection of posts written for the parent who has been trying everything and still feels like they’re failing their child. Every post in this series starts from a moment a parent wasn’t given information they needed, and works back through what the evidence actually says. You can find the full series at nellavosk.com.au/pages/nobody-told-me.

Nobody told me that what came out of my tap could be making my baby’s skin worse.

I had changed the washing powder. I had changed the bath products. I had read the labels on every cream. I had eliminated dairy from my diet while breastfeeding and then reintroduced it, watched for reactions, and found nothing conclusive. And then someone mentioned, in passing, that the water hardness in our area might be contributing to the eczema picture. That the mineral content of the water itself — the calcium and magnesium carbonates that vary significantly across Australian cities — could be affecting my baby’s skin barrier function in the bath, the shower, and in every piece of clothing I washed.

Nobody had mentioned water. Not once.

This post covers two water-related questions that come up constantly for Australian families managing eczema: what hard tap water does to eczema-prone skin, and whether sea water is actually good for eczema — the question every Australian parent asks themselves standing at the beach watching their child play in the waves. Both questions have more nuanced answers than most eczema resources provide.

Can Hard Water Cause Eczema?

Hard water is water with a high dissolved mineral content — primarily calcium and magnesium carbonates, which enter the water supply from the rock and soil through which groundwater passes. Water hardness is measured in milligrams of calcium carbonate per litre (mg/L) or in “degrees of hardness.” Water below 60 mg/L is soft; water above 180 mg/L is considered hard; some areas exceed 300 mg/L.

Hard water does not cause eczema. Atopic dermatitis has a genetic and immunological basis that predates any environmental exposure — as covered in the NTM post on why eczema isn’t caused by something you did. A baby without the genetic predisposition will not develop eczema from hard water exposure. But for babies and children who already have eczema, hard water is a significant and often overlooked environmental factor that can drive the frequency and severity of flares.

How Hard Water Makes Eczema Worse: The Mechanisms

The relationship between hard water and eczema operates through several distinct mechanisms, all of which converge on the skin barrier:

Calcium and surfactant interaction

When hard water contacts soap or detergent, the calcium ions react with the soap to form calcium stearate — a waxy, insoluble compound commonly known as soap scum. On the skin surface, this compound is not fully rinsed away with hard water; it forms a residue that sits on the skin and acts as an irritant. For eczema-prone skin, which already has a compromised barrier and heightened sensitivity to irritants, this residue is a consistent low-level trigger.

This also explains why hard water areas typically require more soap and shampoo to lather — the calcium ions in the water are neutralising some of the surfactant. The residue this creates on eczema-prone skin compounds the irritation.

Direct skin barrier disruption

Research published in the Journal of Investigative Dermatology has demonstrated that hard water applied directly to skin increases its permeability — the extent to which substances can pass through the skin barrier. Elevated water hardness was found to reduce the activity of skin proteases (enzymes involved in maintaining the skin’s outer structure) and to increase skin surface pH, both of which impair barrier function. In eczema-prone skin, where barrier function is already compromised, this additional disruption is clinically significant.

Interaction with filaggrin deficiency

Babies and children with atopic eczema are more likely to have reduced filaggrin expression (the skin barrier protein discussed in the NTM post on eczema causation). Filaggrin breakdown products include natural moisturising factors that help the skin manage its water and pH environment. In filaggrin-deficient skin, the capacity to compensate for hard water’s disrupting effects is reduced. The same hard water exposure that causes minimal impact on intact skin has a more pronounced effect on filaggrin-deficient eczema-prone skin.

The UK ECLIPSE trial evidence

The most significant clinical study on hard water and eczema is the ECLIPSE trial, a large randomised controlled trial conducted across multiple UK sites. The trial investigated whether fitting water softeners in homes of infants with eczema would reduce eczema severity compared to a control group. The results, published in 2021 in the NEJM Evidence journal, found that ion exchange water softeners did not produce statistically significant improvements in eczema severity as the primary outcome, though secondary analysis showed benefits in some subgroups.

This finding is important to understand correctly: the absence of a statistically significant benefit from water softeners in the whole-group analysis does not mean hard water has no effect on eczema. It suggests that water hardness is one of multiple contributing factors, and that addressing it in isolation may be insufficient to produce measurable eczema improvement in an environment where other triggers are also operating. The mechanism by which hard water affects eczema skin is well-established; its clinical significance relative to other triggers varies between individuals.

Water Hardness Across Australian Cities

Water hardness varies considerably across Australia because it depends on the local geology and water source. Here is a general picture of what families in major Australian cities are working with:

• Perth: Moderate to hard. Perth’s water comes from a mix of groundwater and desalinated water. Groundwater sources in the Perth region can be moderately hard (100–250 mg/L), though the mix with desalinated water moderates this. Hardness varies by suburb and changes seasonally with water source.

• Adelaide: Hard. Adelaide has some of the hardest water among major Australian cities, particularly when drawing from the Murray-Darling system. Hardness can range from 150 to over 350 mg/L depending on the source blend at any given time. Families managing eczema in Adelaide frequently cite water hardness as a factor.

• Melbourne: Relatively soft. Melbourne’s water supply comes primarily from high-quality mountain catchments (Thomson, Yering, Upper Yarra), which are naturally low in dissolved minerals. Melbourne water is among the softest of major Australian cities (typically 10–40 mg/L).

• Sydney: Soft to moderate. Sydney’s catchment-sourced water is relatively soft (typically 50–80 mg/L in most areas), though this varies between supply zones.

• Brisbane: Moderate. Brisbane’s water supply draws from multiple sources with varying hardness. South East Queensland Water typically rates Brisbane water as moderately hard.

• Darwin: Moderate to hard, with significant seasonal variation. Dry season groundwater sources are harder; wet season dilution reduces hardness.

To check the specific water hardness in your area, contact your local water authority or check their website — most Australian water utilities publish annual water quality reports including hardness data.

Practical Steps for Hard Water Areas

If you are in a hard water area and managing baby or child eczema, the following approaches reduce the skin contact with hard water minerals without requiring major infrastructure changes:

Bath additives

Adding water softening bath additives (such as sodium bicarbonate, colloidal oatmeal, or commercially prepared eczema bath additives) to bathwater can reduce its effective hardness. Some eczema bath soaks also contain emollient ingredients that compensate for the barrier-disrupting effects of hard water. Bath oil added to the water creates a lipid layer on the skin surface that provides some barrier protection during bathing.

The Nella Vosk article on magnesium baths for eczema covers the specific bath additive approach that many Australian families find helpful for managing eczema-prone skin during bathing.

Bath temperature

Hot water increases the solubility of calcium carbonates, potentially increasing their concentration in the bath and on the skin. Lukewarm bath temperature (36 to 38°C) — already recommended for eczema bathing for its direct effect on inflammation — also reduces the mineral exposure on the skin. The connection between bath temperature, sweating, and eczema is covered in the article on why heat triggers eczema flares.

Emollient application immediately after bathing

Applying an emollient within three minutes of leaving the bath — to damp skin — is the single most effective intervention for compensating for water-related barrier disruption. The emollient replaces the lipids that hard water interaction removes from the skin surface and prevents trans-epidermal water loss as the skin dries. In hard water areas, the prompt application of emollient after bathing is even more important than in soft water areas.

Laundry considerations

Hard water also affects how clothing is washed. In hard water areas, detergent dissolves less effectively, residue is more likely to remain in fabric after washing, and more detergent is typically needed to achieve cleaning. For families managing eczema, this means that the standard guidance to use less detergent and add an extra rinse is particularly important. White vinegar in the rinse cycle (approximately half a cup) can help neutralise mineral deposits in washed clothing. The full guide to eczema-safe laundry in Australia covers the hard water laundry considerations in detail.

Water filtration and softening

Point-of-use shower filters that reduce water hardness are available and may reduce skin irritation during showering and bathing, though the clinical evidence for their benefit in eczema specifically is limited (as the ECLIPSE trial discussed above suggests). Whole-house ion exchange water softeners are the most effective approach to hard water but represent a significant investment. For families in very hard water areas (Adelaide particularly) where eczema is severe and other interventions have been exhausted, a GP or dermatologist referral for a formal assessment of environmental triggers may be warranted.

Is Sea Water Good for Eczema? The Question Every Australian Parent Has

Australia’s coastline and its culture of beach-going means this is a question that comes up in almost every eczema conversation I have with Australian families. The short answer is: it depends, and the full answer is more interesting than either a simple yes or a simple no.

Why sea water might help

Seawater contains sodium chloride at approximately 3.5% concentration, along with magnesium, potassium, calcium, and trace minerals. Several of these have documented effects on eczema-prone skin:

• Magnesium: Research has found that magnesium sulfate solutions can improve skin barrier function and reduce inflammatory markers in atopic dermatitis. The Dead Sea, whose water has extremely high magnesium content (approximately 30 times higher than ocean water), has been studied extensively as a treatment for psoriasis and eczema, with evidence of benefit for both conditions. Standard ocean water has much lower magnesium content, but some effect is plausible

• Antimicrobial effect: Seawater’s salt concentration has some antimicrobial properties that may reduce Staphylococcus aureus colonisation on eczema-prone skin. S. aureus colonisation is present in over 90% of people with eczema and is a significant driver of inflammation and flares

• Temporary itch relief: Many people with eczema report that brief ocean swimming produces temporary itch relief. This may be partly placebo effect, partly the cooling effect of the water on inflamed skin, and partly genuine mineral benefit

Why sea water might harm

For the same reasons that seawater may help, it can also harm — depending on the individual, the skin’s current state, and how the exposure is managed:

• Salt on broken or raw skin burns. If the eczema is currently flaring with broken or weeping skin, sea water contact will cause significant pain and may worsen the inflammatory state. Sea swimming is best reserved for periods of relative skin stability, not active flares

• Sun exposure intensifies the drying effect. Salt water draws moisture from the skin, and Australian sun rapidly increases trans-epidermal water loss from exposed skin. Without immediate rinsing and emollient application after swimming, the net effect on the skin barrier may be negative even when the swimming itself provided temporary relief

• S. aureus re-colonisation: While seawater may temporarily reduce S. aureus on the skin surface, the bacteria recolonise rapidly. If swimming leads to sun-dried, unmoisturised skin, the net effect on S. aureus and skin inflammation may worsen rather than improve

The verdict on sea water and eczema

Sea water is neither reliably beneficial nor reliably harmful for eczema — it is conditional. For many Australian families, brief ocean swims produce a short-term improvement in skin appearance and itch, particularly in the summer months when the cooling effect combines with mineral contact. This benefit is real and worth enjoying when the skin is stable.

The key variables that determine whether sea water helps or harms:

• Current skin state: stable or mildly affected skin generally responds better than actively flaring or broken skin

• Rinse immediately after: rinsing with fresh water after ocean swimming removes residual salt before it dries on the skin and triggers dehydration-related itch

• Apply emollient promptly: within three minutes of rinsing and drying, apply a thick emollient to replace the lipids drawn out by salt water and sun exposure

• Sun protection: protecting eczema-prone skin from extended sun exposure before and after swimming reduces the overall drying and inflammatory burden of a beach day

• Duration: a brief swim is different from spending hours in and out of the ocean with salt drying on the skin repeatedly throughout the day

What the Water Picture Means for Your Eczema Management

Water — both the water you bathe in and the water you swim in — is an environmental variable that many eczema management protocols overlook. It is not the most important variable (that remains consistent emollient use and identified trigger management), but it is worth understanding because it operates every single day in the bathing routine and in the laundry cycle.

The practical summary:

• If you are in a hard water area (Adelaide, parts of Perth, Darwin), water hardness is likely contributing to your eczema management picture. Bath additives, lukewarm temperature, immediate emollient application, and eczema-safe laundry practices are the most accessible responses

• If you are in a soft water area (Melbourne, most of Sydney), water hardness is unlikely to be a significant factor, though emollient timing still matters

• Ocean swimming is conditionally beneficial for many eczema families. Enjoy it when the skin is stable, rinse immediately after, and apply emollient promptly

• What touches the skin after water contact — the towel, the clothing, the cream — matters as much as the water itself. The fabric worn after a bath or swim is part of the water management picture. The guide on eczema-friendly clothing for Australian families covers the full fabric and clothing picture

Keep Reading

These posts connect to the water and environmental trigger picture:

Nobody Told Me My Baby’s Eczema Wasn’t My Fault (Cause vs Trigger)

Nobody Told Me My Baby Was Scratching All Night Without Even Waking Up

Why Heat and Sweat Trigger Eczema Flares

Magnesium Baths for Eczema: What Works and Why

How to Stop Baby Scratching at Night

How to Wash Clothes for Eczema: The Complete Australian Guide

Best Laundry Detergents for Eczema (Australian Guide)

Complete Guide to Eczema-Friendly Clothing for Australian Families

Managing eczema is about reducing the total trigger load, one layer at a time. What your baby wears against their skin every night is one of the most controllable layers. The Bamboo Bubby range is designed to reduce the fabric triggers that compound everything else — heat, friction, moisture — so the skin has less to fight on the nights it matters most.

ABOUT THE AUTHOR

Kelly Northey is a Certified Postpartum Nutrition Professional (CPPNP) and founder of Nella Vosk, the parent company of the Bamboo Bubby range. She has spent fourteen years working with Australian families navigating baby and child eczema — the sleepless nights, the skin that won’t heal, and the guilt of feeling like you should be doing more. The Bamboo Bubby range exists because of those families.
Learn more about Kelly.