Description: Lactic Acid is found in sour milk, hence often called Milk Acid.
Lactic Acid is a strong Alpha-Hydroxy Acid and hence will have excellent exfoliant properties, although these are weaker than, but second only to, Glycolic Acid. AHA products should be a stand-alone treatment product and not included in another product. While AHA can be included in other products there are certain incompatibilities that may arise plus AHAs (because of the pH required for best effectiveness) may not allow other products (such as cleansing masks) to work properly, and vice versa.
Lactic Acid, when compared to Glycolic or Citric Acids, shows greatly reduced irritation while offering pronounced efficacy in exfoliating and skin rejuvenating formulations. When used at concentrations of 2% or less, Lactic Acid will perform; pH regulating, antimicrobial, and moisture-binding functions. When used at concentrations higher than 2%, Lactic Acid will perform the same functions as well as offering:
AHA products should have a pH of 3.5 to 4.5 for best effectiveness (Note at pH 7 AHAs are totally ineffective); while masks have a pH dependant on the function (cleansing masks with a pH of 7 to 8; moisturizing masks with a pH of 5 to 6 and some treatment masks with a pH of 4.5 to 5.5). Hence these may have incompatible pH.
If a product has some film-forming agent or, in the case of masks, have materials which are not absorbed, these may reduce the absorption of AHAs. Hence reduce their effectiveness.
If a mask uses clays then the AHAs will react with these and both reduce the activity of the AHAs and destroy some of the clay.
AHAs are generally a face treatment and not to be confused with a cleanser. You should clean the face first and then apply the AHA treatment.
If you want to use a concentrated AHA then you will find most references suggest Glycolic Acid. However, while this is cheap and obtained in 70% liquid form, because of its apparent activity it has its dangers in that it will quickly burn skin with disastrous consequences.
5 - 20% Lactic Acid would be a good place to start, as this is milder while still having excellent skin peel affects and is not legislated against.
Citric acid is also a widely used organic acidulate, probably because it is classified as a weak acid. As with all manufacturing processes, we recommend lab scale trials in order to determine appropriate quantities. Normally the product is titrated with a dilute solution of Lactic Acid (10 or 20% in water) until the desired pH is achieved. It is preferred as an acidulate as it tends to have less of a destabilizing effect on emulsions than does Citric Acid.