Please note

On this page you'll find scientifically documented findings on the effect of filtered shower water. We also clear up a few myths that unfortunately still get advertised. Further down you'll find a list of the sources cited here.

Hair in focus: structure, colour and shine

Hard water makes hair dry and brittle

In comparative studies of soft and hard water, hair that had been exposed to hard water was found to have lower tensile strength. The mineral build-up can make hair stiffer, which leaves it more prone to mechanical breakage (Srinivasan et al., 2013).

Chlorine can attack the pigment in colour-treated hair

Chlorine, often used for disinfection, acts as an oxidising agent. It can attack the pigment in colour-treated hair and lead to unwanted colour changes (for example a green tinge in light hair caused by copper ions) (Evans et al., 2021).

Healthy scalp and sebum regulation

An accumulation of minerals (build-up) can block the pores of the scalp and contribute to itching or dandruff, because natural sebum regulation is disrupted (Gomes et al., 2017).

Skin in focus: barrier function and potential irritants

Interaction with surfactants (cleansing agents)

Hard water contains high concentrations of calcium and magnesium ions. These react with soaps and surfactants to form so-called "limescale soaps". These residues are harder to rinse off and can irritate the surface of the skin (Arkwright et al., 2020).

Effect on the pH value

Studies show that washing with hard water can briefly raise the pH value of the skin's surface. A disturbed pH balance is associated with a weaker skin barrier and increased dryness (Danby et al., 2018).

Prevention where there is an atopic predisposition

There is evidence that early exposure to hard water can increase the risk of infants developing atopic eczema. Reducing the limescale load is therefore being discussed as a preventive approach (Perkin et al., 2016).

Filtering out chlorine and heavy metals

Chlorine by-products

Warm water releases chlorine vapours while you shower. Inhaling trihalomethanes can irritate the airways of sensitive people. Activated carbon filters are able to reduce these volatile organic compounds (VOCs) significantly (Xu and Weisel, 2003).

Heavy metals from pipes

In older buildings, lead or copper from the household pipes can get into the shower water. KDF filter media use electrochemical oxidation/reduction to bind these metals in the filter medium and so reduce the load on skin and hair (Kim et al., 2015).

Myths

"Filters cure skin conditions such as atopic dermatitis."

False. Shower filters are not medical devices. They can, however, reduce irritating factors (chlorine, limescale), which supports your basic skincare and can ease symptoms. A cure cannot be promised, either legally or medically.

"Filters remove 100% of all bacteria."

Partly true. Some filter media do inhibit bacterial growth (they act bacteriostatically), but they are no substitute for sterile treatment. In Germany, though, tap water is microbiologically very safe anyway.

"The filter lasts forever"

False. Filter media are consumables. Once the binding capacity (of the activated carbon, for example) is used up, the effect wears off. Changing the filter regularly (usually every 2–3 months) is essential for hygiene and effectiveness.

List of sources