Cosmetics Formulation Development

If using 3 skin care products Divided into 3 steps: 1. Toner 2. Essence 3. Serum - All 3 steps need to put DMI3% for all 3 or just some. For example, enter DMI3% only in the toner. - If you enter some steps At what step do you recommend it? Thank you in advance

Hello, you can use all 3 formulas, but I recommend you to consider the active ingredients of the formula. For example, if the toner is only water + Glycerin is optional. สารนำพา , as it does not contain any active substances that must be absorbed into the skin, inserting สารนำพา in this case would be wasted.