EDTA, Ethylenediaminetetraacetic acid is a molecule which complexes metal ions in aqueous environments. It is available in four neutralizations, two of which, Disodium EDTA and Tetrasodium EDTA, are commonly used in the cosmetics.
Generally, the choice of which product to use is determined by the pH of your product, but this is not a hard and fast rule. Disodium EDTA is commonly used in neutral to mildly acidic products, like most creams, lotions, and neutral pH liquid soaps and shampoos. EDTA works synergistically with your preservative to improve preservative efficacy.
Disodium EDTA has limited solubility in water, but at a typical usage rate of 0.2% to improve preservative efficacy, even if not fully solubilized, it is still efficacious.
Cosmetic manufacturers frequently use this ingredient for a variety purposes. It primarily works as a preservative, chelator and stabilizer, but has also been shown to enhance the foaming and cleaning capabilities of a cosmetic solution. As a metal chelator, it counteracts the adverse effects of hard water by binding with heavy metal ions contained in tap water, which in turn prevents the metals from being deposited onto the skin, hair and scalp.
This makes it a particularly useful ingredient for rinse-off products that inherently require water to come into contact with the skin. Essentially, this ingredient deactivates the metal ions through bonding with them, which in turn prevents cosmetic products from deteriorating, maintains its clarity and prevents it from smelling rancid.
You can find this ingredient in virtually every personal care product including facial moisturizer/lotion, sunscreen, anti-aging treatment, cleanser, shampoo/conditioner, hair dye, body wash and eye cream