The scalp itches after showering – this phenomenon is not a coincidence, but the result of a chemical reaction that occurs millions of times a day in German bathrooms.
Imagine your scalp is a delicate garden. Every day, you water this garden with water you consider pure. But what if this water is full of invisible "weed killers"?
This is exactly what happens when hard water hits your scalp. German tap water has an average hardness of 15-25 degrees Celsius—rich in calcium and magnesium ions. Combined with shampoo surfactants, this creates insoluble soap residue that forms a film on your scalp.
"Hard water reduces the skin's ability to retain water," explains Dr. Petra Hoffmann, a dermatologist at the University Hospital of Hamburg. "The minerals disrupt the skin's natural barrier function and lead to dryness, irritation, and chronic itching. "