The pH level of the skin surface of adults is about 4.5 to 5.5 and increases with age to about 6.
Are skin care preparations with a low pH level of about 4 reasonable for the older skin?
After external influence of media with pH levels differing from the pH level of the skin surface, the skin activates its protective function (barrier). This applies to pH changes to lower, acidic levels but also to higher or alkaline pH levels. After extreme pH impacts, the skin recovery works at full blast. Key words: fruit acid peeling (acidic) and alkaline cleansing. Barrier damages may appear if the application is too extended, though.
To minimize risks and extend the timeframe for fruit acid peelings, the fruit acids can be equipped with acidic buffers (salts), as for instance in the form of partly neutralized citric or phosphoric acid. In this case, buffers can adjust the preparations to a fixed, less acidic pH and keep it stable against external influences. The timeframe should not be overextended though as otherwise similar damages may occur as with unbuffered acids.
In analogy, already pH levels between 7 and 8 will cause skin damages in the case of extended contact with alkaline buffered media.
The skin has its own weak buffer that helps to quickly re-adjust its initial pH level after the application of unbuffered, pH neutral, slightly acidic or slightly alkaline preparations. Hence unbuffered skin care preparations with a low pH such as 4 only have little impact on the pH of the skin surface.
Dr. Hans Lautenschläger