Disodium EDTA is an ingredient used in shampoos, moisturizers, cleansers, and other personal care products as a chelating agent to improve product stability.
EDTA stands for ethylenediaminetetraacetic acid, which is also referred to as edetic acid. This compound was first synthesized in 1935 by Ferdinand Münz from the combination of ethylenediamine and chloroacetic acid. Today, EDTA is primarily synthesized from ethylenediamine, formaldehyde, and sodium cyanide. EDTA is produced as several salts, notably disodium EDTA and calcium disodium EDTA. It exists as a colorless, water-soluble solid.
EDTA and its salts were initially developed for specific industrial use, such as the prevention of calcium in hard water from causing staining or other problems in textile printing. During the Second World War, research was carried out on sodium salts of EDTA in order to determine whether these would be useful as an antidote to poison gas. Research established that EDTA contained a highly effective antidote to heavy metal toxicity (lead poisoning, for example), since it chelated just as well with lead as it did with calcium when it was infused into the bloodstream, and without any side effects.
The use of EDTA and its salts has since expanded to cosmetics, personal care products, medications, and even food. You can find disodium EDTA in almost every type of personal care product, including facial creams and lotions, sunscreens, anti-aging treatments, cleansers, shampoos, conditioners, hair dye, body wash, eye creams, and more.
One of the functions of disodium EDTA is as a chelating agent. The Personal Care Product Council’s online ingredient dictionary defines chelating agents as, “ingredients that complex with and inactivate metallic ions to prevent their adverse effects on the stability or appearance of cosmetic products.” Thus, disodium EDTA works by first binding to metal ions, such as Ca2+ and Fe3+, which subsequently inactivates them. After being bound by EDTA into a metal complex, metal ions remain in solution but exhibit diminished reactivity.
You may be wondering why we need to worry about binding metal ions in cosmetics. Well, it turns out that metallic impurities can come from many different sources. For instance, the ingredients themselves, especially those that are naturally derived, may have metallic impurities. Additionally, the water system or minute extractions from metallic equipment and storage containers may contain impurities. If not deactivated, these metallic ions can deteriorate cosmetic products by reducing clarity, compromising fragrance integrity and causing rancidity.
In cosmetics and personal care products, the binding of metal ions helps to prevent deterioration and protects the integrity of skin care products from undergoing unwanted consistency changes, pH changes, odor changes, or texture changes. Thus, disodium EDTA can be classified as a preservative. In addition, when binding with calcium, iron, or magnesium, disodium EDTA results in enhanced foaming and cleaning abilities.
Another function of disodium EDTA is to bind heavy metal ions and trace elements contained in tap water, which prevents these metals from being deposited onto the skin, hair, and scalp. While hard water is not harmful to your health overall, it can have a huge effect on your hair and skin. Hard water can lead to product build-up in hair, cause color-treated hair to wash out very quickly, and make hair more prone to breakage. Similarly, hard water makes it difficult to rinse away soap from the surface of your skin, leaving your skin dry and potentially irritated. Thus, disodium EDTA can help to counteract these adverse effects of hard water. This function of disodium EDTA makes it a particularly useful ingredient for rinse-off products that inherently require water to come into contact with the skin.
The Food and Drug Administration (FDA) reviewed the safety of disodium EDTA and approved the use of this ingredient as a food preservative for direct addition to food.
The safety of disodium EDTA was assessed by the Cosmetic Ingredient Review (CIR) Expert Panel. Based on the available data, the CIR Expert Panel found that these ingredients are safe as used in cosmetics and personal care products.
Clinical tests have shown that standard concentrations of the ingredient do not irritate, sensitize, or penetrate the skin. Despite these findings, disodium EDTA has been shown to enhance the dermal penetration of other ingredients contained in a product. Therefore, caution must be used if disodium EDTA is formulated with other ingredients that could be potentially harmful if absorbed by the skin.
References: Wikipedia, “Ethylenediaminetetraacetic Acid”, Healthy.net, “Chelation Therapy, The History of EDTA”, Cosmetics & Toiletries, “Deciphering Chelating Agent Formulas”, 2013, L’Oreal Paris, “Disodium EDTA”, Truth In Aging, “Disodium EDTA”, Culligan Water, “Effects of Hard Water on Hair and Skin”, Int J Toxicol. 2002;21 Suppl 2:95-142.