Reviewed November 11, 2026
Chlorine and Swimming Hair: What Actually Damages It, and What Fixes It
The green tint is the giveaway, and the giveaway is wrong. Everyone blames chlorine, because chlorine is the chemical they can smell. The green is copper, oxidized to Cu2+ ions binding to cystine and cysteic acid in the keratin. Experiments in 1978 proved it cleanly: copper alone turned hair green, chlorine alone did not. The copper comes from pool algaecides and from corroded copper pipes and heat exchangers in the pool system, and it binds to the same sulfur sites chlorine exposes. Knowing which chemical did the damage decides which treatment removes it.
Chlorine's real job is subtler and worse. Hypochlorous acid, the active form of chlorine in pool water, is an oxidizing agent with a pH of 7.5 to 8.0, and it attacks the hair's outer lipid layer, the 18-MEA layer that makes the fiber hydrophobic. When that layer is stripped, the cuticle swells, the scales lift, and the cortex underneath absorbs water like a sponge. The shaft dries out, turns brittle, and starts to break with the kind of friction a comb used to handle easily. Blonde, grey, and chemically processed hair show the damage first, because the cuticle is already lifted and the porous fiber absorbs more of everything.
The copper, and what removes it
The green tint needs a chelating agent, not a purple shampoo. Purple shampoo deposits violet pigment to cancel yellow tones, and it does nothing to copper. Chelating agents bind metal ions and lift them off the keratin: tetrasodium and disodium EDTA, sodium phytate, and the copper-selective agents histidine and EDDS, effective around 0.025 to 0.25 percent. The honest limit is that EDTA at about 0.1 percent in most products is a formula stabilizer, not a hair treatment dose, so a standard shampoo with EDTA on the label is not a copper treatment. A dedicated chelating shampoo or a salon chelating treatment is what actually removes the metal.
Prevention is cheaper than the fix, and it is a sequence, not a single step. Pre-saturate the hair with fresh tap water before swimming, so the fiber absorbs clean water instead of pool water. Apply a leave-in conditioner or a light oil to the lengths, which forms a barrier the pool chemicals have to cross. Wear a swim cap, even a loose one, because it cuts the exposure time even when it does not seal. And rinse with fresh water immediately after getting out, before the pool water dries on the fiber and concentrates the chemicals in it.
What cannot be repaired
The damage chlorine does to the shaft is permanent, because the shaft is dead protein. No product fuses it back together, and no treatment restores a stripped lipid layer. What repair means, in practice, is three things: remove the copper with a chelating treatment, fill the gaps with protein and moisture treatments so the fiber bends instead of snapping, and trim the ends that have already split, because a split end travels up the shaft if you leave it. The new growth comes in undamaged, and the damaged length grows out. That is the whole repair program, and anyone selling a faster one is selling a mask.
Keep reading: Heat Protectant and the 185 Degree Line: What the Lab Data Says, Bond Builders vs Protein Treatments: Different Damage, Different Fix, and Split Ends: Why Trimming Still Beats Every Repair Claim cover the nearby cases in this series.
Frequently asked questions
Does chlorine turn hair green?
No. The green tint is copper, oxidized to Cu2+ ions binding to keratin. Experiments in 1978 showed copper alone turned hair green while chlorine alone did not. The copper comes from pool algaecides and corroded pipes.
Does purple shampoo remove green tint from swimming?
No. Purple shampoo deposits violet pigment to cancel yellow tones. It does not bind or remove copper. A chelating shampoo with EDTA, phytate, histidine, or EDDS is what removes the metal.
How do I protect my hair before swimming?
Pre-saturate it with fresh tap water, apply a leave-in conditioner or light oil to the lengths, wear a swim cap, and rinse with fresh water immediately after getting out. Each step cuts the chemical exposure.
Can chlorine damage to hair be repaired?
The damage to the shaft is permanent, because hair is dead protein. Repair means removing the copper, filling gaps with protein and moisture treatments, and trimming split ends. New growth comes in undamaged.