Please note

On this page you'll find scientifically backed insights into the effects of filtered shower water. We also debunk some commonly advertised myths. Below you'll find a list of the sources referenced here.

Focus on hair: Structure, color and shine

Hard water makes hair brittle and prone to breakage.

Comparative studies between soft and hard water found that hair exposed to hard water has lower tensile strength. The mineral deposits can lead to increased stiffness, making the hair more susceptible to mechanical breakage (Srinivasan et al., 2013).

Chlorine can damage the pigmentation of dyed hair.

Chlorine, often used for disinfection, acts as an oxidizing agent. It can attack the pigmentation of colored hair and lead to undesirable color changes (e.g., a greenish tint in light hair due to copper ions) (Evans et al., 2021).

Healthy scalp and sebum regulation

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

Focus on skin: Barrier function and irritation potential

Interaction with surfactants (cleaning 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 more difficult to rinse off and can irritate the skin's surface (Arkwright et al., 2020).

Influence on pH value

Studies show that washing with hard water can temporarily raise the pH level of the skin surface. A disrupted pH balance is associated with a weakened skin barrier and increased dryness (Danby et al., 2018).

Prevention in cases of atopic predisposition

There is evidence that early exposure to hard water may increase the risk of developing atopic eczema in infants. Therefore, reducing calcium levels is being discussed as a preventive approach (Perkin et al., 2016).

Filtration of chlorine and heavy metals

Chlorine byproducts

When showering, warm water produces chlorine vapors. Inhaling trihalomethanes can irritate the respiratory tract of sensitive individuals. Activated carbon filters are able to significantly reduce these volatile organic compounds (VOCs) (Xu and Weisel, 2003).

Heavy metals from pipelines

In older buildings, lead or copper can leach from the plumbing into the shower water. KDF filter media use electrochemical oxidation/reduction to bind these metals within the filter medium, thus reducing exposure to skin and hair (Kim et al., 2015).

Myths

"Filters heal skin diseases such as neurodermatitis."

Incorrect. Shower filters are not medical devices. However, they can reduce irritating factors (chlorine, limescale), which supports basic hygiene and can alleviate symptoms. A cure is neither legally nor medically guaranteed.

"Filters remove 100% of all bacteria."

Conditional. While some filter media inhibit bacterial growth (have a bacteriostatic effect), they do not replace sterile treatment. In Germany, however, tap water is already very safe from a microbiological perspective.

"The filter lasts forever"

Incorrect. Filter media are consumables. Once the binding capacity (e.g., of activated carbon) is exhausted, its effectiveness diminishes. Regular replacement (usually every 6 months) is essential for hygiene and effectiveness.

Detailed list of sources