The concentration of AHA commonly used in the
cosmetic formulations is 10% or less. Topical application of AHA in this concentration range leads to
loosening and reduction of excess layer of dead cells,
gradually revealing a fresher and smoother-looking
skin. Nevertheless, the amount of AHA that should
be penetrated into skin to cause high effectiveness with low irritation has never been clarified.
It is likely that higher AHA concentration in the
formulation leads to higher penetration of AHA
into skin and consequently results in higher effciency [30]. Thus, the formulation of CC4.5 : 0.5 may
be suitable for acting as the rate-controlling matrix
in the patch containing natural AHA as it gave the
highest release of tartaric acid and a constant supply
at a certain level for a specific time (120 min after application). However, the optimum concentration
of AHA released from the patch within the favourable duration (for example, within 30 min) should
be further studied and developed to improve the effciency and increase the safety of using patches in
cosmetics.