How To Keep Hair Safe during Hair Straightening

Hair straightening involves applying heat to the hair inorder to break the disulphide bonds between keratin. This allows hair to be re-shaped and straightened by passing through the flat irons of the straightener.

What temperature is ideal for hair health during straightening?

Exposing hair to very high temperatures is definitely not the best thing to do. But in my quest to identify safe maximum temperatures for hair, I could not find any good resource on other websites. So, I searched for a research paper that tries to quantify the damage caused to hair due to hair straightening. I found a paper titled “The effect of various cosmetic pretreatments on protecting hair from thermal damage by hot flat ironing” published in the journal of cosmetic science, which tries to address this issue.

Effect of heat on hair

Many people wish to have Shiny and Straight hair. This kind of hair is generally considered attractive and gorgeous. But what makes hair shiny or straight?

  • Shiny hair
  • The shine in hair is because of the outermost layer of hair called the cuticle layer. Shine is produced by light being reflected off of hair. So, the smoother the surface of hair, the shinier it appears.
    This layer also acts like a barrier and protects the inner layers. The job of cuticle layer is to keep the inner layers safe. The inner layers consist of cortex and medulla which we will see next.

  • Straight hair
  • Hair straightness is decided by the arrangement of keratin in the cortex. Cortex is the layer that produces the strength to the hair. Curly or Straight hairs are decided by the shape of cortex. The keratins are bonded together through disulphide bonds. The shape of hair can be modified by rearranging the keratin molecules which requires the disulphide bonds to be broken. Hair straighteners work by breaking these bonds. When hair is passed through the hot plates of a flat iron, the heat breaks some of the bonds between keratin and hair becomes ready to accept a new shape. The flat iron rearranges the keratin to give hair a straighter shape.

How do achieve shiny and straight hair while keeping hair healthy

Research conducted by Zhou, Y., et al measures the damage caused to the cuticle layer and the cortex. Some of the main results of their research are

  • Pores in cuticle layer
  • They show that high thermal treatment causes pores and breakdown of cells in the cuticle layer.

  • Damage to Keratin layer
  • They also show that degradation of hair keratin occurs due to thermal treatment above 205°C. The degradation further increases with the increase of temperature.

  • Breakage of hair
  • The damage to hair has a combined effect of weakening and making hair more susceptible to breakage during combing and other grooming activities.

  • Pretreatment with polymers
  • The damage to hair is reduced by pre-treating hair with polymer based substances or hydrophobic units reduces damage. By applying a barrier between hair and heat, the damage to hair can be considerably reduced. It reduces the damage to the cuticle and reduces cracks and holes caused from over heating. This in turn helps increase shine and overall health of your hair.

How to protect hair during straightening

So, with this knowledge, we can make an informed decision on which type of hair straighteners are best for our hair. There are two most important things to keep in mind when straightening your hair

  • Use a thermal protection spray
  • AlwaysUse a thermal protection spray or cream for your hair. This will provide a barrier to the heat by forming a film layer on hair. This will help in reducing hair damage both to the outer cuticle and the inner layers. Some of the products available are :


  • Use the lowest temperature for your hair
  • The temperature required for all hair types are different. So, based on your hair type, use the lowest possible temperature. That is why it is necessary to buy straighteners where the heat can be adjusted. But, this feature is usually only available in higher end straighteners. Some straighteners that allow adjusting heat are



    There are some other resources available which give you tips on keeping your hair safe during straightening process. This post on huffington has some tips; teenvogue has a list of most common mistakes everybody make. Tartan explains some of the scientific details behind hair straightening.

    Making an informed decision in buying a quality hair straightener will help you have shiny and straight hair for a long time.

    References :

    Zhou, Y., et al. “The effect of various cosmetic pretreatments on protecting hair from thermal damage by hot flat ironing.” Journal of cosmetic science 62.2 (2010): 265-282. A pdf copy is available at ncbi and at scconline

    The views expressed here are mine. Please do your research before making any decisions.

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