Most swimmers notice what chlorine does to their hair long before they understand why it happens. The straw-like texture. The colour that fades faster than it should. The scalp that feels tight and itchy after every session. These are predictable consequences of repeated chlorine exposure without an adequate management routine, and understanding the mechanism makes it much easier to address.
Hair is not a uniform structure
Hair looks simple but is structurally layered. The outermost layer, the cuticle, is made up of overlapping cells arranged like roof tiles along the hair shaft. These cells protect the inner cortex, which determines the hair's strength and elasticity. The cuticle surface is coated with lipids that give hair its natural lustre, its ability to repel water, and its resistance to damage.
When those surface lipids are intact and the cuticle cells lie flat, hair feels smooth, looks shiny, and handles mechanical stress well. When they are disrupted, the cuticle cells lift and separate, the hair feels rough and dry, it tangles more easily, and it becomes significantly more vulnerable to breakage.
What chlorine does to the hair shaft
Chlorine attacks hair through two primary mechanisms. First, it dissolves the surface lipids that protect the cuticle, exposing the underlying structure to direct chemical and mechanical damage. Second, it can break down the disulphide bonds in the keratin proteins that give hair its structural integrity, weakening the shaft from within.
Friction from moving through water compounds both effects. As the cuticle cells lift in response to chlorine exposure, they create a rougher surface that increases the friction between individual hairs during movement. That rougher surface also allows hypochlorous acid to penetrate more deeply into the hair shaft, which is why damage accumulates disproportionately with training frequency. The more you swim without managing it, the more rapidly the next session damages the hair.
The cumulative result, in swimmers who train regularly without an adequate routine, is the classic straw-like texture that comes from progressive shaft weathering rather than any single damaging session.
Colour change and green hair
Colour change in swimmers is well supported by research. Chlorine degrades melanin over time and accelerates surface weathering of the hair shaft, both of which contribute to colour fading. For swimmers with colour-treated hair, the effect is faster and more pronounced because chemically treated hair already has a more disrupted cuticle structure going into the pool.
UV exposure adds a second damage pathway for outdoor pool swimmers and open water swimmers, degrading hair proteins, lipids, and pigment independently of chlorine.
Green hair is worth addressing specifically because it is commonly misattributed to chlorine. Chlorine does not turn hair green. The actual cause is copper deposition from pool plumbing and fittings. Copper is present in most pool water in small amounts, and it binds to the hair shaft, producing a greenish tint that is most visible in light or bleached hair. Chlorine and pre-existing shaft damage make that deposition more likely by opening up the hair structure, but the green colour itself comes from copper, not chlorine.
What chlorine does to the scalp
The scalp is a distinct skin environment with a high density of hair follicles, abundant sebaceous glands, and its own microbiome. Chlorinated water disrupts this environment in ways that go beyond the general skin barrier effects described elsewhere in this series.
Chlorine and chloramines strip the scalp's natural oils, alter its pH, and reduce its ability to retain moisture. The result is a scalp that feels tight, itchy, and sometimes flaky after sessions. For swimmers with sensitive or atopic scalps, this reaction can be more pronounced and harder to manage. For those prone to dandruff or seborrhoeic dermatitis, repeated disruption of the scalp's microbial balance can worsen existing conditions.
The pre-swim routine for hair
The most effective hair protection is layered. Before getting in the pool, wet your hair thoroughly with fresh water. Hair that is already saturated absorbs significantly less chlorinated water during the session than dry hair does. The physics are straightforward: the hair shaft can only hold so much water, and if it is already full of fresh water, there is less capacity for pool water to penetrate.
If you are not wearing a cap, apply a leave-in conditioner or light oil to the lengths of your hair before swimming. This provides a physical barrier that reduces direct chlorine contact and friction damage during the session. Skip this step if you are wearing a cap, as conditioners and oils on the hair will cause it to slip.
Wearing a swim cap meaningfully reduces chlorine exposure and friction for the hair, even though it does not keep the hair completely dry. For frequent swimmers, it is worth the habit.
The post-swim routine for hair
Rinse hair and scalp with fresh water immediately after getting out of the pool. Do not wait until you get home. That immediate rinse removes residual chlorine, chloramines, and dissolved metals from the hair shaft and scalp before they continue their work.
Follow with a swimmer-specific shampoo formulated to remove chlorine and pool chemistry from the hair. Standard shampoos clean the hair but do not address the specific chemistry left behind by pool water. A swimmer-specific formula includes ingredients that actively bind with and remove chlorine rather than simply washing around it.
Follow the shampoo immediately with a conditioner to restore lubrication and help flatten the cuticle. For swimmers training at high frequency, a deeper conditioning treatment used several times a week will help offset the cumulative damage that regular pool exposure creates.
Premax De-Chlorine Shampoo is formulated to remove chlorine and pool chemistry from the hair without the aggressive stripping that harms the cuticle. Follow with Premax Post-Swim Conditioner to restore moisture and smooth the hair shaft.
