Jennifer is suspicious about sodium hydroxide: I keep reading that sodium hydroxide is a real skin irritant, yet I keep seeing it in quite a few high-end skin products (Peter Thomas Roth’s “Unwrinkle” pads, fourth on the ingred. list and La Roche-Posay eye cream). I know that it is regularly used to change the pH of the product. What I do not know is should I avoid it like the plague? Or is it ok in small amounts? I keep reading conflicting things, so I thought I would finally turn to you!
You are absolutely right, Jen. But you’re also totally wrong. Allow us to explain.
What is Sodium Hydroxide
Sodium hydroxide (or NaOH as we chemists like to call it) is a very powerful alkaline, or basic, material. That means it has a pH that is so high that it can be corrosive to skin. So you’re right that it can be a skin irritant. It’s a primary ingredient in lye soap and in hair relaxers.
But NaOH is really only hazardous when used in high concentration in its pure form. In most products it’s reacted with an acid so it’s neutralized to form a harmless salt. The two skin care products you cited are good examples of formulas that are not harmful applications of NaOH.
Peter Thomas Roth
First, let us say that we LOVED this guy in Van Halen. Second, we’re not concerned about his use of NaOH in his Unwrinkle Pads. Even though it’s the 4th ingredient on the list, it’s probably just used to bring up the pH of his multi-acid formula. (Very low pH can be just as bad for your skin as very high pH.) Here are the ingredients for those of you who are interested in stuff like this:
WATER (AQUA), GLYCOLIC ACID, ETHOXYDIGLYCOL, SODIUM HYDROXIDE, SODIUM LACTATE (LACTIC ACID), ROSA CENTIFOLIA FLOWER WATER, HAMAMELIS VIRGINIANA (WITCH HAZEL) WATER, PPG-5-CETETH-20, BUTYLENE GLYCOL, ARGININE, LINOLENIC ACID (VITAMIN F), GAMMA-AMINOBUTYRIC ACID, TOCOPHEROL (VITAMIN E), RETINOL (VITAMIN A), CHOLECALCIFEROL (VITAMIN D), ALANINE, SODIUM ASCORBYL PHOSPHATE (VITAMIN C), ZINGIBER OFFICINALE (GINGER) ROOT EXTRACT, CITRUS MEDICA LIMONUM (LEMON) PEEL EXTRACT, CHAMOMILLA RECUTITA (MATRICARIA) FLOWER EXTRACT, SYMPHYTUM OFFICINALE LEAF EXTRACT, CAMELLIA SINENSIS LEAF EXTRACT, ALOE BARBADENSIS LEAF JUICE, SALICYLIC ACID, CAPRYLIC/CAPRIC, TRIGLYCERIDE, PROPYLENE GLYCOL, METHYLPARABEN, PROPYLPARABEN, DIAZOLIDINYL UREA
Ring around La Roche-Posay
We couldn’t find a La Roche product labeled “eye cream” that contained sodium hydroxide, but we did find La Roche-Posay Redermic Eye Cream which contains potassium hydroxide a very close cousin of sodium. In this product it’s probably there just to neutralize the thickening agent. Many cosmetics are thickened with acrylic acid-based polymers that require neutralization with a base like NaOH. Here are the ingredients:
(Aqua) Water, Glycerin, Cyclopentasiloxane, Ascorbic Acid, Propylene Glycol, Isohexadecane, Silica, PEG/PPG-18/18 Dimethicone, Alochol Denat., Nylon-12, Potassium Hydroxide, Sodium Styrene/MA Copolymer, Madecassoside, Sodium Hyaluronate, Disodium EDTA, Acrylates Copolymer, Tocopherol, Isobutane, Phenoxyethanol, Sodium Benzoate, Methylparaben, Propylparaben.
The Beauty Brains bottom line
Sodium hydroxide is nasty stuff, no doubt. But just because a chemical can be harmful in it’s concentrated form doesn’t mean it can’t be used responsibly. NaOH is totally safe when it’s used to neutralize acids at the appropriate levels. So unless you’re Sammy Hagar, you have no reason to fear Peter Thomas Roth.