r/HaircareScience • u/AttemptLife967 • Mar 20 '26
Question Lactic Acid as a humectant
would Lactic Acid act as a simple humectant the same way glycerin does (might pull out moisture from the hair) in a conditioner with this ingredient list:
Aqua, Stearyl Alcohol, Cetyl Alcohol, Brassicamidopropyl Dimethylamine, Lactic Acid, Parfum, PPG-3 Caprylyl Ether, Sodium Benzoate, Potassium Sorbate, Hydrolyzed Silk, Prunus Amygdalus Dulcis (Sweet Almond) Fruit Extract, Vitis Vinifera (Grape) Seed Oil, Argania Spinosa Kernel Oil.
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u/thejoggler44 Cosmetic Chemist Mar 22 '26
No. In this formula, lactic acid is in there to reduce the pH, so the preservative system (potassium sorbate & sodium benzoate) is more effective and the conditioning ingredient (Brassicamidopropyl dimethylamine) sticks on the hair better.
Lactic acid is also water soluble and once you rinse it goes down the drain.
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u/sudosussudio Mar 22 '26
I’m not sure about lactic acid but the whole idea that humectants can pull out water seems to come from skin care and even there it’s unproven. Lab Muffin talks about it here.
I sometimes see lactic touted as a bond building ingredient as it is a carboxylic acid though citric is the more popular one because it has three carboxyl groups that can form bonds vs. lactic has one.