Chlorine in the shower is a burden for sensitive skin, skin conditions and hair structure. Chlorinated shower water, however, is a much more complex issue. In waterworks, the chlorine added to drinking water reacts with organic matter and microorganisms, forming, among other things, trihalomethanes – such as chloroform – and many other halogenated compounds. With proteins it forms chloramines. Some of it naturally remains dissolved in the water as a mixture of highly reactive hypochlorites and hypochlorous acid. Chlorine, or rather hypochlorites, and other harmful substances enter the body in two ways – through absorption by the skin and by inhaling aerosols and gases. We will look at chloroform in a future article. Here we focus on the effect of so-called free chlorine.
Why and for whom is chlorine in the shower harmful?
Chlorine, or hypochlorites, protect water from bacterial contamination. They kill bacteria, so we can be sure that the water we drink is clean – and we also shower in it.
For some people, however, especially those with sensitive skin or skin conditions, this residual chlorine can be a problem. It is undoubtedly irritating, and in conditions such as atopic eczema it is a real problem. Because free chlorine is highly reactive, it is mostly “used up” on the surface of the skin and does not penetrate the body. Its effect is therefore mainly local.
For healthy skin, the effect of low concentrations is usually small.
In people with atopic, dry or damaged skin, hypochlorites can cause:
- burning and itching,
- a feeling of tight skin,
- worsening of eczema,
- increased transepidermal water loss.
A study in the Journal of Dermatology
In an experimental study (1), water with free chlorine from 0.5 mg/l reduced the water-holding capacity of the stratum corneum in patients with atopic dermatitis; in healthy subjects a statistically significant effect appeared only at 2 mg/l.
The study was small – 20 atopic patients and 10 controls – so it is supporting rather than conclusive evidence.
What people call a “chlorine allergy” is therefore most often irritant dermatitis or a worsening of existing eczema, not a classic allergic reaction. A significant part of the problems can also be caused by hot water, long showers, soap, fragrances or hard water.
How to protect yourself from chlorine? Filters for chlorinated water
For those who suffer from any of the problems above (women and small children usually have more sensitive skin), we recommend treating the water before showering with a suitable shower filter for chlorinated water. I would consider removing free chlorine sensible especially if a person:
- suffers from atopic eczema or very dry skin,
- regularly experiences itching, burning or redness after showering,
- has sensitive eyes or airways,
- uses very hot water and takes long showers,
- has a poorly ventilated bathroom,
- notices that the problems subside with non-chlorinated water.
With hives, however, it is necessary to check whether they are triggered by heat, the water itself or cosmetics.
Filters for chlorinated water – KDF or activated carbon?
There are 2 types of chlorine filters on the market:
- Filtration with KDF media, or a combination of KDF and calcium sulphite – KDF is a special mixture of metals that reduces chlorine electrochemically. KDF is consumed very slowly during the reaction. Final polishing is done by calcium sulphite, which reacts with chlorine extremely quickly and removes it from the water practically completely.
- Activated carbon filtration – needs relatively long contact time to remove chlorine from water, which is very questionable in a small filter with a flow rate of 10 l/min. As soon as the active sites on the surface of the carbon grains are occupied – which happens very quickly – the chlorine filter starts to lose efficiency rapidly. You can then no longer rely on the water being of good quality with all free chlorine removed.
That is why we prefer the electrochemical reaction combined with final polishing, which gives a chlorine filter a service life several times longer than activated carbon. For removing residual chlorine, the combination of KDF and calcium sulphite used in the H2O nanotec IMT-J2 shower filter is much better and more reliable.
It is important to be clear about what we can realistically expect from a filter for chlorinated water. Shower filters for free chlorine such as the H2O nanotec IMT-J2 can bring:
- less chlorine smell,
- less irritation and drying of the skin,
- better tolerance of showering in sensitive people,
- less eye irritation,
- subjectively nicer skin and hair.
We certainly do not present it as a treatment for eczema or allergies or as cancer prevention, as you can sometimes read. Nevertheless, the benefits of such a chlorine filter are considerable, especially for sensitive people and in areas where water has to be chlorinated more heavily for various reasons. In those cases we really do recommend a filter for chlorinated water.
Written by:
RNDr. Jiří Polman CSc., Managing Director
References:
- (1) Seki T., Morimatsu S., Nagahori H., Morohashi M.: Free residual chlorine in bathing water reduces the water-holding capacity of the stratum corneum in atopic skin. J Dermatol. 2003
