Can Tap Water Make Eczema Worse?

Around one in five children in the UK has eczema, and it affects a significant number of adults too. If you live in London, the South East, or any of the many hard water areas across England, you may have noticed that your skin flares up more than friends in different parts of the country. That is not coincidence.

The relationship between tap water and eczema is real, it is documented in peer-reviewed research, and it involves two distinct mechanisms: the hardness of the water — specifically its calcium and magnesium content — and the chlorine added as a disinfectant. Understanding which matters more in your case points towards very different solutions.

The hard water and eczema connection

Hard water contains dissolved calcium and magnesium — minerals that come from the rock the water passes through before it reaches the treatment works. In soft water areas, typically upland regions in Wales, Scotland, the north of England, and parts of the South West, there is little of this dissolved mineral content. In hard water areas — which cover most of England including all of London, the South East, East Anglia, the Midlands, and Yorkshire — mineral levels are significantly higher.

Researchers at the University of Sheffield and King's College London have found that hard water damages the skin barrier. When hard water is left on the skin — after washing, showering, or bathing — the calcium deposits interact with the natural fats in the skin, disrupting the protective lipid layer. This leaves skin more permeable, more prone to drying out, and more susceptible to irritants and allergens penetrating the surface. For people with eczema, whose skin barrier is already compromised, this is a meaningful aggravating factor.

A 2017 study published in the Journal of Investigative Dermatology found that children living in hard water areas were 87% more likely to have eczema at age one than those living in soft water areas. A subsequent clinical trial — the SWET trial — tested whether installing water softeners in the homes of children with eczema improved their symptoms. The results were encouraging for families, with many reporting improvement, though the trial was not powered to show a statistically significant effect across the full group. The research remains ongoing.

Chlorine and skin sensitivity

All UK water companies add chlorine or chloramine to drinking water as a disinfectant. This is essential — it kills bacteria and keeps water safe from the treatment works to your tap. The concentrations used are well within safety limits and cause no harm to most people. But for those with sensitive skin or eczema, daily exposure to chlorinated water in the shower can strip the natural oils that protect the skin, leaving it drier and more reactive.

This is not the same as a chlorine allergy — true chlorine allergy is extremely rare. What most people describe as a chlorine reaction is an irritant response: the detergent-like effect of chlorine on the skin's lipid layer, repeated daily. People with atopic dermatitis are more sensitive to this because their skin barrier is already partially impaired.

Chlorine levels in tap water vary by supplier and by how far your home is from the treatment works — properties further away in the network tend to receive water with lower residual chlorine. If you notice a strong chlorine smell from your shower, your supply is likely at the higher end. A shower filter addresses this specifically and is a low-cost intervention worth trying before committing to a whole-house solution.

How hard is your water?

Water hardness is measured in milligrams of calcium carbonate per litre (mg/L CaCO3). Soft water is below 60 mg/L, moderate hardness is 60–120 mg/L, hard water is 120–180 mg/L, and very hard water is above 180 mg/L. London tap water typically measures 250–300 mg/L — among the hardest in the UK. Much of the South East is similarly hard.

Check your exact area on the UK water hardness map — enter your postcode to see your hardness level and how it compares to the national average. Your postcode report also includes a full water quality summary.

Shower filters for eczema

If chlorine is a significant irritant for your skin, a shower filter is the most targeted and affordable solution. KDF-55 (a copper-zinc alloy medium) and vitamin C (ascorbic acid) filters both neutralise free chlorine in shower water. KDF-55 is the most common technology in shower filter showerheads; vitamin C filters are used in some inline designs and are particularly effective at removing chloramine as well as chlorine.

Shower filters do not remove hardness minerals — calcium and magnesium ions are not affected by KDF or carbon filtration. If hard water is your primary concern, a shower filter will not significantly reduce limescale or the mineral deposits that affect your skin barrier. That requires a water softener.

Shower Filter

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Premium option — KDF-55 filtration in a brushed-steel design

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Shower Filter

AquaBliss SF220 Shower Filter

Budget option — multi-stage filtration at a fraction of the cost

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For a full comparison of shower filter options, see our best shower filter guide.

Whole-house solutions for severe cases

For families with severe eczema who live in hard water areas, a whole-house water softener is the most comprehensive approach. A water softener uses ion exchange resin to swap the calcium and magnesium ions responsible for hardness with sodium ions. The result is soft water from every tap and shower throughout the home, with none of the mineral deposits that aggravate sensitive skin.

The main drawbacks are cost — a quality installed softener runs £800 to £2,500 — and the requirement for a plumber to install it and ongoing salt top-ups. Softened water is also slightly higher in sodium, which means it is not recommended for drinking in homes with very young babies, and some people find it leaves a slightly slippery feel on skin. Most households use a separate unsoftened drinking water tap.

See our best water softener guide for a full comparison of the leading UK models, including which areas benefit most. You can also check your hardness level on the UK water hardness map to see whether your area justifies the investment.

Frequently asked questions