Skin care products, cosmetics and beauty products by law, are required to be pH-compatible with human skin. However, many substances, including most tap water, can upset the skin's natural pH balance. Low cabin humidity is a primary cause of jet lag. Avoid alcohol and caffeine. Most of the Earth's water is not pH-correct and contains minerals which dehydrate the skin.
Most tap waters contain heavy minerals and chemical purifiers, with a pH in the alkaline range.
Softeners lower the alkalinity but do not neutralize it. Tap water can also leave a drying residue that interferes with skin functioning and with topical skin care products. Their purpose is to seal in existing moisture. There are countless beauty and skin care products on the market because, like fingerprints, no two people's skin is alike. The darker your skin the more oil it contains, making it more difficult for your complexion to maintain the ideal skin moisture content.