Hello
Propanediol does not irritate the skin. Can be used up to 100%, but according to the information on the web page Which is stated at the highest 20% is the number provided by the manufacturer. which is a level suitable for general use Using more than 20% may cause severe skin discomfort. but from the nature of the formula as informed by the members The formula owner uses 95% for the reason that they want
Propanediol completely dissolves ALA in the formulation. to achieve full efficiency