Summer accumulates three distinct chemical attacks on the hair fiber: UV radiation, chlorine from swimming pools and sea salt. Each follows a specific degradation mechanism and requires appropriate protective actives. Effective summer protection is not based on a generic product but on understanding these three distinct chemistries. Hairswiss analyzes them.
UV and hair photo-degradation: molecular mechanism
UV-B (280–315 nm) and UV-A (315–400 nm) radiation induces two types of degradation on the hair fiber. UV-B acts directly on keratin chemical bonds through photo-oxidation of tryptophan and cysteine residues: tryptophan absorbs at 280 nm and generates free radicals that trigger a cascade of disulfide bridge oxidation. UV-A degrades eumelanin (responsible for black-brown hair) and pheomelanin (blonde-red) through oxidative photobleaching — hence the natural “lightening effect” in summer.
UV-damaged keratin shows an increased cysteic acid content (irreversible oxidation product of cysteine, measurable by HPLC) and a reduced water contact angle on the cuticle — indicator of degradation of the surface 18-MEA lipid film. Photo-degraded keratin protein is more porous, mechanically more fragile and more sensitive to subsequent aggressions (heat, coloring).
Chlorine: direct oxidation of disulfide bridges
Chlorine used in swimming pools is present in aqueous solution as hypochlorous acid (HClO) and hypochlorite ions (ClO⁻), in a pH-dependent equilibrium (pH 7.2–7.6 in standard pools). HClO is a powerful oxidizer (E° = +1.49 V) that preferentially attacks the disulfide bridges (S–S) of cuticle keratin by direct oxidation:
S–S + HClO → S(O)–S (sulfoxide) → SO₃⁻ (sulfonate at completion)
This oxidation is irreversible: sulfonates cannot reform disulfide bridges. Each prolonged pool exposure structurally degrades the cuticle, increases hair porosity and accelerates discoloration of treated hair.
Sea salt: osmosis and dehydration
Seawater contains on average 3.5% NaCl (osmotic concentration ~600 mOsm/kg). The hair fiber being a medium with variable water content (~10–15% residual moisture), immersion in saltwater creates an outward osmotic gradient: water exits the fiber toward the surrounding hypertonic solution by osmosis, accompanied by rapid dehydration of the hair cortex.
On drying, NaCl crystals precipitate in and on the fiber. These orthorhombic structure crystals exert mechanical pressure on the cuticle scales, lifting them by volumetric expansion and increasing the differential fiber porosity — resulting in an irregular, rough surface prone to amplified hygroscopic frizz.
Protective actives: chemistry and efficacy
Capillary UV filters
Cosmetic capillary UV filters are either organic absorbers (Benzophenone-4, Ethylhexyl Methoxycinnamate) that absorb UV energy and dissipate it as heat, or mineral diffusers (TiO₂, ZnO nano) that reflect radiation. Tocopherols (vitamin E, particularly α-tocopherol) are free radical scavengers that neutralize reactive oxygen species generated by photo-oxidation.
Film-forming anti-chlorine agents
Hydrolyzed proteins (keratin, wheat proteins) and film-forming silicones (dimethicone 50–100 cSt) form a physical protection film on the cuticle, reducing HClO access to active sulfur sites. Lipophilic oils with unsaturated fatty acids (argan, macadamia) reconstitute the surface 18-MEA lipid film, reducing wettability and limiting chlorine and salt penetration.
Anti-osmotic humectants
Glycerin and low molecular weight hyaluronic acid (HA), applied before exposure, create a favorable internal osmotic gradient by increasing the concentration of hydrophilic molecules within the fiber. This pre-saturation reduces the magnitude of osmotic dehydration at sea.
Professional summer protection products on cliCHair
Argan Native Fluid — Edelstein
Edelstein’s Argan Native Fluid constitutes a natural lipid shield against summer aggressions. Its richness in tocopherols (α-tocopherol, ~620 mg/kg) provides measurable antioxidant activity against UV-generated free radicals. Its oleic (43%) and linoleic (36%) fatty acids reconstitute the 18-MEA lipid film eroded by sea salt and chlorine. To be used as a pre-sun treatment or as a finishing step after shampooing.
→ Argan Native Fluid on cliCHair.ch
Intensive Remedy Keratin Spray — Edelstein
Edelstein’s leave-in keratin spray combines hydrolyzed keratin, olive oil and Behentrimonium Methosulfate in a no-rinse formulation. The hydrolyzed keratin forms a peptide film that physically reduces chlorine and UV access to the cuticle’s critical sulfur sites. Ideal applied before the pool or beach for colored or weakened hair.
→ Intensive Remedy Keratin Spray on cliCHair.ch
Hairswiss takeaway
Summer hair protection is not a superficial cosmetic field — it is a chemistry of structural damage prevention. UV, chlorine and sea salt act through three distinct pathways (photo-oxidation, direct S–S oxidation, osmotic dehydration) that mutually potentiate each other. Effective protection combines UV filters, reconstituting lipid film and pre-saturation humectants — applied before exposure, not after. Hairswiss monitors the evolution of photo-protective actives used in professional hair care formulations.