Swimming and Hair Protection: How Chlorine and Salt Water Damage Hair and What to Do About It

How Chlorine Damages Hair

Chlorine (sodium hypochlorite) in swimming pools serves as a disinfectant. The same oxidising chemistry that kills bacteria also affects hair keratin.

The mechanisms of chlorine damage:

Protein degradation: Chlorine oxidises the disulphide bonds within the keratin protein structure. These bonds are what give hair its strength and elasticity. Breaking disulphide bonds produces progressively weaker hair that stretches rather than bounces back and eventually breaks.

Cuticle lifting: Chlorine raises the hair cuticle pH, causing scales to lift and remain partially open. Open cuticle scales produce roughness, frizz and increased porosity. Damaged cuticle scales also allow moisture to enter and escape rapidly.

Colour damage: Chlorine oxidises melanin (the hair's natural pigment) and also affects artificial colour molecules. Blonde hair is most visibly affected (chlorine does not turn hair green; copper from plumbing interacts with chlorine and deposits on the hair, producing the green cast visible in some regular swimmers).

Sebum removal: Chlorine strips the natural oil coating from the hair shaft more effectively than most shampoos. This leaves the hair dry and brittle after each swim session.

Cumulative damage timeline: Occasional swimming produces minimal permanent damage if proper care is applied. Regular swimming (3 or more sessions weekly) without protection produces measurable changes in hair structure within 4 to 6 weeks, including increased porosity, reduced tensile strength and visible brittleness.

How Salt Water Damages Hair

Salt water (ocean water) contains sodium chloride at approximately 3.5% concentration plus minerals including magnesium, calcium and potassium.

The mechanisms:

Hygroscopic drying: Sodium chloride is hygroscopic (it draws moisture toward itself). Salt on the hair shaft draws moisture out of the cortex into the surrounding environment after swimming, leaving the hair dehydrated and brittle.

Mineral deposition: Calcium and magnesium from sea water deposit on the hair shaft, creating a coating that reduces flexibility and contributes to the "rough" feel of hair after ocean swimming. These mineral deposits can also interfere with product absorption until removed.

Tangling: The combined effect of drying and mineral deposition causes significant tangling and matting, particularly in curly and coily hair types.

The texture change from salt water: The "beachy wave" texture that salt water produces is real and is caused by the hygroscopic salt drawing moisture unevenly from different sections of the hair, causing some sections to contract and wave while others do not. This texture is attractive in the short term but the underlying dryness is damaging with repeated exposure.

Pre-Swimming Hair Protection

The Wet Hair Technique

Hair that is already saturated with clean water absorbs significantly less chlorinated pool water or salt water. The hair shaft has a limited water-holding capacity; filling it with tap water first leaves less space for chlorine or salt water to enter.

How to apply: Wet your hair thoroughly with tap water before entering the pool or ocean. The hair should be visibly wet and feel heavy with water. Apply conditioner or a protective oil over the wet hair for additional barrier protection.

Why this works: Research on material porosity shows that pre-saturated porous materials (including hair) absorb foreign liquids at significantly reduced rates compared to dry porous materials.

Protective Coating Products

Applying a coating before swimming creates a physical barrier between the water and the hair shaft.

For pool swimming:

• Silicone-based leave-in conditioners: Silicone forms an effective barrier against chlorine penetration. Apply to thoroughly wet hair before swimming.
• Coconut oil: Applied to wet hair, coconut oil's protein-affinity properties may reduce the degree of protein loss from chlorine oxidation. It also creates a partial hydrophobic barrier.
• Dedicated swim hair products (TriSwim, UltraSwim): Specifically formulated to create a chlorine-resistant barrier.

For ocean swimming:

• A moisturising leave-in conditioner: Counteracts the hygroscopic drying effect of salt
• A heavy sealant oil (avocado, castor): Provides an additional barrier against mineral deposition

Swim Cap

The most effective protection for the hair shaft is a well-fitting latex or silicone swim cap. A cap worn correctly keeps most pool water away from the hair entirely.

The limitations: Caps do not keep the hair completely dry (water enters at the edges). Wearing a cap over very thick or long hair requires a larger-sized cap or a different style. Some people find caps uncomfortable for long training sessions.

For natural and textured hair: A satin-lined swim cap or a large silicone cap worn over a satin cap provides both the waterproof barrier and protection from friction damage inside the cap.

Post-Swimming Hair Care

Rinse immediately after leaving the water. Every minute of post-swim delay allows chlorine and salt to continue interacting with the hair. Rinse with fresh water (shower or fresh water source) within 10 minutes of swimming.

Use a chelating or clarifying shampoo once weekly: Regular shampoos do not remove mineral deposits from pool or ocean water. A chelating shampoo (containing EDTA, citric acid or phytic acid) removes mineral build-up. Products: Malibu C Crystal Gel Treatment, Joico Colour Balance Blue Shampoo (also chelating), Ion Swimmer's Shampoo.

Apply a deep conditioner after every swim: The combination of chlorine or salt exposure plus rinsing produces a dryness cycle that a rinse-out conditioner alone does not fully address. Apply a deep conditioner for 5 to 10 minutes after swimming, even for quick post-swim care.

Protein treatment monthly for regular swimmers: The protein degradation from chlorine warrants a monthly protein treatment (Olaplex No. 3, K18, Aphogee Two-Minute Reconstructor) to restore some disulphide bond integrity between swimming sessions.