Topic
Swimming, chlorine and green hair
Heavy swimming can strip and discolour hair, and green tints usually come from copper rather than chlorine itself.
Key takeaways
- Heavy swimming can strip and discolour hair. Among 67 Japanese national-team swimmers, 61% had hair discoloration versus 0% of 54 age-matched controls. The golden hair showed complete loss of cuticle, fewer and smaller melanosomes (pigment granules), lower sulfur and detectable chlorine in the cortex. Nanko 2000
- The proposed mechanism is that friction against water removes the cuticle and hypochlorous acid in pool water then penetrates and oxidises the pigment. Nanko 2000 That describes elite athletes training for hours, not a recreational dip.
- Green hair is usually copper, not chlorine. Case reports link green tints in blond hair to copper from household or pool water. Predisposing factors are previous damage (mechanical, sun, bleaching, dyeing, waving), frequent chlorinated water and alkaline shampoos. Described treatments include chelating shampoos (EDTA), hydrogen peroxide, D-penicillamine shampoo and hydroxyethyl diphosphonic acid. Mascaro 1995
- Pool chlorine and bleach damage are the same kind of chemistry (oxidation), so bleached or coloured hair is at highest risk (reasoning; see bleach and colour damage).
- No trial shows that pre-wetting hair or wearing a swim cap prevents damage. These are plausible, low-risk ideas.
The science
The Nanko study measured sulfur loss (consistent with oxidation of cystine) and chlorine in the pigment granules. The control group was non-swimmers, so exposure time and chlorine cannot be separated from friction and sun. Nail damage coexisted in the swimmers. Nanko 2000 Evidence on ordinary recreational swimming is lacking.
What it means for your hair
- Blond, light, bleached or coloured hair has the most visible discoloration and green-tint risk.
- High-porosity hair absorbs more water, chlorine and copper (reasoning).
- Curly and coily hair gets drier. A leave-in conditioner before swimming is common practice but untested.
- Hard-water homes add copper and mineral deposits to the risk.
Myths and facts
- Myth: chlorine turns blond hair green. Copper deposits do, and chlorinated water helps copper bind to damaged hair. Mascaro 1995
- Fact: swimmers' golden hair showed actual structural loss, not just surface staining.
Bottom line
Rinse hair with fresh water before and after swimming. Apply conditioner or oil beforehand and shampoo soon after (practice advice, not trial-backed). If you swim often or have hard water, an occasional chelating or clarifying shampoo helps with copper. Cover your hair with a cap for long training sessions.
Studies 2
Nanko H et al. Hair-discoloration of Japanese elite swimmers. J Dermatol. 2000
Result: 61% of swimmers had hair discoloration versus 0% of controls; affected hair had lost its cuticle, had fewer melanosomes, less sulfur and detectable chlorine.
Read the study ↗Mascaro JM Jr et al. Green hair. Cutis. 1995
Result: Green tints in blond hair came from copper in household or pool water, favoured by prior hair damage, chlorinated water and alkaline shampoos.
Read the study ↗Related
- Bleach and colour damageBleaching and permanent dyeing chemically damage the hair fibre in every hair type, and most of that damage cannot be undone.
- UV and sun damage to hairSunlight fades colour and weakens hair through free-radical damage, with light, bleached and coloured hair most affected.
- Hair damage: what it is and where it comes fromDamage is cumulative and cannot be biologically healed, and chemical treatments, heat, sun, water and grooming each add to it.