EDTA

EDTA is a chelating agent. This is just a fancy way of saying it grabs onto metal ions and holds them so they don't cause trouble.

Trace metals like iron, copper, and calcium sneak into products through water and raw materials. These metals make oils go rancid, cause color and texture changes, and stop preservatives and cleansers from doing their job properly.

EDTA locks them up so it's a neat little background helper ingredient.

Typical use is under 2% but numbers as high as 10-25% have been reported in hair color products.

The Cosmetic Ingredient Review panel looked at the whole family and concluded they're safe as used. At cosmetic concentrations, they have not been found to be skin irritants or sensitizers.

Clinical testing has found no absorption through skin so the scary-sounding oral toxicity numbers from animal studies aren't relevant to a face cream.

One real formulation note: this ingredient is a penetration enhancer so it can slightly increase how much of the other ingredients get through (though this is more of a thing for formulators to work around).

Allergy is genuinely rare; there are a handful of case reports so be sure to avoid if you're patch test positive to EDTA.