Encyclopedia · chelator
Disodium EDTA
The classic cosmetic chelator, which grabs calcium, magnesium, iron and copper so shampoos lather and keep in hard water, with no clinical hair trials of its own.
What it is
Disodium EDTA is a salt of ethylenediaminetetraacetic acid, used at low levels in shampoos, conditioners and colour products to bind metal ions. It also boosts preservatives and prevents rancidity and discolouration.
How it works
It wraps metal ions in a soluble complex. On hair, that could help remove or block calcium and copper deposits, which are linked to stiffness, dullness and oxidative damage (Godfrey 2013; Smart 2009; Millington 2020).
What the studies show
- A safety assessment of EDTA and its salts found cosmetic skin exposure gives systemic levels far below toxic oral doses. Inhalation from aerosols was the concern, and EDTA may increase penetration of other chemicals. The panel found them safe as used (Lanigan 2002).
- In a lab study of UV damage to hair, copper-doped white hair produced more hydroxyl radicals under wet UVA than undoped hair (Millington 2020).
- In over 300 women from 9 countries, calcium, magnesium and copper rose from root to tip, and people who rated their hair health as poor had higher metal levels (Godfrey 2013).
- Imaging of coloured hair washed in tap water showed calcium concentrated in the sulfur-rich layers of the cuticle, and copper uptake can add to damage during later colouring (Smart 2009).
The hair-benefit evidence is indirect. Metals on hair are linked to oxidative damage and poorer perceived hair health, and chelators are the mechanistic remedy, but we found no clinical trial of an EDTA shampoo on hair outcomes.
Side effects and safety
The safety assessment above found EDTA and its salts safe as used in cosmetics, with the caveats about increased penetration of other substances and inhalation of aerosols (Lanigan 2002).
Bottom line
A useful silent helper in hard-water areas, and not something to seek out or avoid for hair health. Chelating-shampoo marketing often relies on higher chelator levels or acids, and the benefit remains unproven in trials. Whether EDTA at normal shampoo levels meaningfully reduces hair calcium is unknown. See hard water and hair.
Studies 4
Lanigan RS et al. Final report on the safety assessment of EDTA, calcium disodium EDTA, diammonium EDTA, dipotassium EDTA, disodium EDTA, TEA-EDTA, tetrasodium EDTA, tripotassium EDTA, trisodium EDTA, HEDTA, and trisodium HEDTA. 2002
Result: Cosmetic skin exposure gives systemic levels far below toxic oral doses; inhalation from aerosols was the concern; may increase penetration of other chemicals; the panel found EDTA and its salts safe as used.
Read the study ↗Millington KR et al. UV damage to hair and the effect of antioxidants and metal chelators. J Cosmet Sci. 2020
Result: UV damage to hair was affected by antioxidants and metal chelators in the lab.
Read the study ↗Godfrey S et al. Metals in female scalp hair globally and its impact on perceived hair health. 2013
Result: Calcium, magnesium and copper rose from root to tip, and women who rated their hair health as poor had higher metal levels; hardness ions were higher in people who coloured their hair. Unilever-affiliated authors; an association only.
Read the study ↗Smart KE et al. Copper and calcium uptake in colored hair. 2009
Result: Calcium concentrated in the sulfur-rich layers of the cuticle of coloured hair; copper uptake can add to damage during later colouring.
Read the study ↗Related
- Tetrasodium EDTAThe more alkaline, more soluble EDTA salt, with the same chelating job as disodium EDTA and wide use in clarifying and chelating shampoos.
- Tetrasodium glutamate diacetateA biodegradable, glutamic-acid-based chelator marketed as a greener EDTA replacement, with essentially no hair-specific data.
- Sodium phytateA rice- or corn-derived chelator used in natural shampoos as a preservative booster and iron and copper binder, with no hair trials.
- Citric acidThe most common pH adjuster in shampoos and conditioners and, in a 2025 lab study, a calcium-removing treatment that strengthened chemically treated hair.
- Hard water and hairHard water leaves calcium on hair and can irritate skin, but there is no good human evidence that it causes hair loss, and chelating shampoos are untested in trials.