54 HAIR TREATMENT
25 20 15 10 5 0
-5
-10 -15 -20 -25
No treatment ¶
-19.3% Placebo
ActivoilTM Kerox-ProTM
Figure 6: Effects of the lipophilic active upon exposure of the hair to heat treatments. Natural dark brown hair tresses were exposed to 80 strokes of a straightening iron set at 230°C without any treatment (No treatment) or after being applied with a placebo (Placebo) or a formulation containing the lipophilic active (Activoil Kerox-Pro). Total light reflectance (shine) was calculated as the ratio between directional and diffuse reflected light. ** p < 0.001 compared to No treatment and Placebo; ¶ p > 0.05 compared to No treatment.
coherent with an antioxidant action of the lipophilic active. Such action is likely to extend to the preservation of more structural constituents of the hair fibres such as the cuticle keratin and the CMC lipids. In addition to alter the biochemical integrity of the hair fibre, radiation also impacts its ultrastructure. SEM directly informs of the hair surface topography and more specifically on the cuticle cell cohesion. A normal hair shaft displays a typical cuticle arrangement with cuticle cells overlapping each other along the longitudinal shaft axis. An overall transversal wave-line pattern can also be observed at the tip of cuticle cells (Fig 5A, B). Dyed hair tresses were treated with a placebo mask lotion or one containing the lipophilic active before exposure to radiation. Placebo-treated hair tresses show a disorganized cuticle cell arrangement upon radiation. Indeed, the stress caused some cuticle cells to detach from the hair fibre (Fig 5 C, D, E). Furthermore, the wave-line pattern is lost to the profit of a straighter line compatible with broken, shortened cuticle cells. Treatment with the lipophilic active completely protected the cuticle ultrastructure from the exposure to radiation (Fig 5 F, G, H).
In that experiment, radiation was not the
only stress hair tresses were exposed to. Tresses used in that study were previously dyed (step necessary to monitor colour variation) using a permanent dye – a category representing 80% of the hair dye market. Permanent dyes contain alkalising agents that open up the cuticle to favor penetration of dye molecules into the cortex.14
Figure 7: Repairing effect of the lipophilic active from heat damage. Natural dark brown hair tresses were used as is (No treatment) or exposed to 80 strokes of a straightening iron set at 230°C (Heat). Heat exposed tresses were treated with a formulation containing the lipophilic active (Heat+Activoil Kerox-Pro). Total light reflectance (shine) was calculated as the ratio between directional and diffuse reflected light and expressed as arbitrary units (au). * p < 0.05 compared to No treatment; ** p < 0.005 compared to Heat; ¶ p > 0.05 compared to No treatment.
lipophilic active as described in Figure 5 was on hair fibres that sustained chemical (high pH), pro-oxidative (H2
O2 ) and a wide
spectrum radiation stresses. This extends the positive action of the lipophilic active to numerous hair conditions and/or damage. Although almost omnipresent on earth, UV is not the only radiation hair must cope with. Infrared light from the sun is another ‘thermal’ radiation that can target hair. High temperatures can also be generated during hair grooming daily routines. As heat is another stress factor the hair is exposed to, we have verified the ability of the lipophilic active to protect hair from straightening iron-induced damage. Exposure of hair to air dryers and straightening irons have shown to cause various damage. Lipid decomposition, loss of tensile strength and shine have been reported.11,15
Because of the high Furthermore, an oxidising agent is
necessary to transform pigment precursors into high molecular mass colourful complexes. Therefore, the action of the
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temperature they are set to (>200°C), straightening irons can cause a ‘flash evaporation’ of the moisture present in the hair fibre forcing cuticle destabilisation.16 The ensuing lifting of cuticle cells disrupts the smooth surface of the hair fibre causing a shift from a specular light reflection to that of a more diffused manner ultimately leading to a loss of shine. Eighty strokes of iron plates adjusted to 230°C caused a loss of shine on untreated hair tresses or despite after a treatment with a placebo formulation (Fig 6). However, treatment with the formulation containing the lipophilic active ingredient active not only prevented the heat-induced loss of shine but further increased it. This result supports the ability of the lipophilic active to maintain the integrity of the cuticle and F-layer configurations important for the hair shine.
There is no cell renewal in the hair fibre itself once it has grown beyond the follicle.
Conclusion The hair is directly exposed to solar radiation and other environmental factors. In addition, it is prone to the deleterious action of various chemicals, repeated washings and heat exposure that are all part of many daily routines. This will ultimately provoke hair weathering involving oxidative reactions and structural alterations. To cope with such stress factors, the hair possesses its own physical and antioxidant protection systems namely the cuticle and the pigments, respectively. Furthermore, the outermost surface of the cuticle is covered by the F- layer made of 18-MEA fatty acids that create a hydrophobic mantle around the hair fibre. However, photodegradation, thermo- degradation, chemical and pro-oxidative insults involve considerable changes to the outermost F-layer, the cuticle, the lipid cell membrane complex matrix and the pigments internally located in the cortex. Loss of hair ultrastructure, shine, tensile
September 2018
This is in opposition to the epidermis where the stratum corneum is constantly replaced via keratinocyte migration and terminal differentiation. Therefore, as the hair grows, it is exposed to various stresses and prone to weathering. In fact, the apperance of the distal portion of a 15 cm long hair fibre is the testimony of 12 months of damage accumulation. This led us to verify the repairing ability of the lipophilic active. In this experiment, hair tresses were
directly exposed to the straightening iron without any prior treatment. The heat stress caused a significant reduction in hair shine (Fig 7). Treating the heat-damaged tresses with a formulation containing the lipophilic active completely re-established the hair shine. The lipophilic active most likely helps repairing the cuticle structure as well as the F-layer integrity.
+38% +18.4% ** +27%
5 4 3 2 1 0
No treatment ** ¶ –20% *
Heat
Heat + ActivoilTM Kerox-ProTM
Light reflectance variation (%)
Light reflectance variation (au)
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