They might show up as slightly acidic or slightly alkaline because of this. The pH scale measures how strongly acidic or alkaline a solution is using a set of values from pH 0 to pH 14.

Sel:pH is another example—it's a line that focuses on what you need to keep skin at its optimal pH. Your skin functions best at slightly acidic pH levels of 4.5 to 5.5, but that number can vary ...