Why is my hair dry
Why is my hair dry

THE MOISTURE MYTH

Moisturisation of the hair is a cosmetic term that has been historically misunderstood by consumers.   Because the word moisturisation is derived from the term moisture, most consumers understand the term to relate to the water content of the hair fibres.

The term moisturisation is a scientific term defined by the percentage of water that makes up the individual hair fibre, but moisturisation in consumer terms relates to the feel and appearance of the hair.  Scientists have been able to demonstrate that the perception of moisturised hair is not related to the actual moisture content of the hair, it is related to the smoothness of hair.

PERCEPTION OF MOISTURISED HAIR DOES NOT REFLECT ACTUAL MOISTURE

Davis and Sofel asked participants of their study to rate hair for levels of moisture.  The participants judged hair with the highest water content to be the least moisturised.  This discrepancy between the expected feel of moisturised hair and hair with a high degree of moisture is related to the increased friction between hairs that contain a higher level of water when compared to hair fibres that had a lower water content.  Hair with a high-water content feels rough and dry because this makes the hair swell and opens the protective cuticle layer.

The scientists went on to test the participants reaction to hair that had been shampooed compared to hair that had been shampooed and conditioned.  Hair that had been conditioned was deemed to be more moisturised although both hair samples had the exact same moisture level.  This demonstrates consumer perception of moisturisation is not related to the moisture content of the hair fibre.

WHY DOES MY HAIR FEEL DRY?

The consumer deems moisturised hair as a smooth hair fibre with low friction between other fibres.  The cuticle contains the cell membrane complex, the glue that holds all the cells together.  It is made up of structural lipid and protein structures.

The smooth silkiness we equate with moisturised hair, is actually from hair cuticle layers sealed in a fatty complex including fatty acids, ceramics, glycolipids and cholesterol.  One important fatty acid within the cuticle layer is called 18-methyl eicosanoic acid (18-MEA).  18-MEA is bound to the epicuticle which is the thin outer layer of the hair cuticles. This is lipid rich area is also referred to as the external protective f-layer (fatty layer) of hair.

Hair often loses its protective fatty layer when exposed to detergents or during chemical treatments. As the fatty layer is lost, the hair becomes hydrophilic (water-loving) and the cuticles are exposed to further damage.  Healthy hair is hydrophobic (water-hating) and mostly repels water.

KEEPING YOUR FATTY LAYER WHERE IT NEEDS TO BE…

Some products are designed with molecules that can mimic the behaviour of the fatty layer. By imparting some level of hydrophobicity and controlling the moisture absorption into hair; these molecules can protect hair against further frictional damage and make hair manageable.

Structural fats are removed from the cuticle by agents that work to lift the cuticle such as shampoo, hair dye or hair relaxers.  The removal of internal fats leaves holes and vacant areas in the cross-sections of the hair fibre.  The removal of these components renders the intracellular regions more susceptible to rupture, cracking fragmentation resulting in the splitting of the fibre.

Duvel and Wertz et al found the concentration of fats are higher at the roots of hair and lower at the tips of human hair fibres.  They were also to demonstrate the tensile strength of the hair was reduced due to the progressive loss of structural fats.  High cleaning shampoos with anionic surfactants remove surface oils increasing inter-fibre friction making clean hair more difficult to comb.

Some tips for hair that feels hydrated:

  • Tie hair up at night with a silk scarf or use a silk pillow
  • Use a low sulphate or sulphate free shampoo
  • Reduce the use of heated tools when styling your hair
  • Use a microfiber towel to dry your hair
  • Check your vitamin and mineral status to ensure the hair structure is robust
  • Treat hair carefully during styling

THE FINAL WORD

If your hair feels dry, avoid attempting to force water into the fibre with lengthy conditioning treatments or by steam treatments.  To avoid hair that feels dry and rough, look after your hair cuticle to keep your fatty layer in place.

REFERENCES

  1. Water, hydration, and health. Nutrition Reviews, 68(8), p. 439–458.
  2. Skin: Basic Structure and Function, Pages 1134-1144. s.l.:Academic Press.
  3. Six to eight glasses of water still best. NHS.