High alkalinity (pH of 9-14) depletes your skin of vital, natural fats or lipids, which are part of your acid mantle. It erodes your skin’s structure, demolishing hydration that is crucial to the health of your skin. The defensive barrier (acid mantle) breaks down, leaving your skin open to infection without proper hydration to self-repair. Your skin may be too alkaline if it is dry, tight and/or dull in appearance. Classic soaps are too alkaline and body/deodorant soaps should never be used on your face.
When your skin is too acidic (pH of 0-4), it becomes red, oily and pimply. It will often appear greasy, feel irritated and react sensitively. Breakouts, irritation and acne can happen when the skin is too acidic. Acidic skin can result from using a cleanser made with acidic solutions like lemon juice (common in DIY cleansers). Home remedies can also be risky if these items have a pH level far different from that of your skin.
Tap water has a pH of 7 (neutral) which means cleansing and splashing your face with faucet water can leave your skin unbalanced, especially with the high lead contents being discovered in some municipalities water supply systems.