Do hair straighteners damage hair? -

Do hair straighteners damage hair?

Hair straightening involves either: a break in the chemical bond that maintains the structure of keratin in its original form; or a more permanent solution using chemicals The temporary solution involving rapid drying of the hair with an application of a hot iron to shape the strand only lasts until the hair is wet again. […]

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Last updated: Feb 24, 2020

Hair straightener damaging hair
Hair straightening involves either:

  • a break in the chemical bond that maintains the structure of keratin in its original form; or
  • a more permanent solution using chemicals

The temporary solution involving rapid drying of the hair with an application of a hot iron to shape the strand only lasts until the hair is wet again.

Heat Treatments and Changes in Hair Structure

One thing that needs to be taken into account when it comes to straightening hair or any kind of heat treatments is the hair’s natural moisture content. Heat styling will absorb the hair’s moisture, which is essential to its health and beauty. Most stylists suggest using steam producing straighteners to help maintain moisture in your hair if you feel like it may lack it.
However, if you think that this means styling your hair wet will protect it from damage, you are wrong. The hair needs to be steam straightened only after it has been dried. If the hair is wet, it will literally boil in its own moisture content which will cause permanent damage. That said there are products available nowadays that can be used on wet hair.

But Does Straightening Damage Your Hair?

It seems that there are more and more studies showing how hair straighteners cause damage due to the extremely high temperature they may reach. One study (Sarginson et al, 2013) showed that some hair straighteners are a serious household fire hazard as they can reach 220 Celsius and can cause deep burns when not handled properly. Another study (Dussaud, Rana and Lam, 2013) showed that some flat irons can reach temperatures of 250 Celsius. This means that when reaching their maximum heat, they will not only damage your hair but may also damage your scalp skin causing serious burns.

Damage to Hair Structure

Besides accidental heat damage, hair straighteners can cause damage to the structure of your hair, leaving you with less than a silky smooth look. The same study shows an experiment with an automated hair iron; while controlling the gliding speed as well as the heat the hair was ironed at temperatures from 120°C to 175°C and washed between treatments. The results showed that using a temperature of approximately 154°C seemed to maintain hair integrity even with prolonged use of this straightening method. Although temperatures over 200°C showed faster and more permanent results the hair’s wet elasticity and integrity decreased.
The study also concluded that the use of silicone with low temperature hair straightening can offer results comparable to using high heat hair straightening due to the fact that silicone treatment enhances the slip between fibres and keeps them in a more aligned formation. However, using silicone does not protect against heat damage. (p.12)

Damage to Color

It seems that heat treatments on human hair do not just affect the hair’s inner health, but also the way it looks. A study showing the effects of curling irons, which are used in a similar manner to flat irons, shows that hair exposed to temperatures that range from 130°C to 164°C for various periods of times ranging from a few seconds to 15 minutes showed that hair color reacts differently as the treatment decomposes the hair chromophores. For example there was an increased yellowness and darkening of bleached hair. (McMullen and Jachowicz, 1998)

Hair Loss

Hair straightening can be an excellent beauty trick but constant hair straightening at high temperatures as well as using chemicals to aid the straightening process can lead to permanent hair loss. Setting the temperature right and avoiding overuse are just a few of the steps needed to prevent damage. Excessive heat styling causes the scarring of the follicles, but this is not an immediate result, and customers may be using the same detrimental technique over and over again until their hair shows signs of damage. Once hair loss occurs, the scarring may be so severe that the change could be permanent.

Customer Safety Issues

How can customers protect themselves when it comes to the heat they are using for straightening their hair? The logical answer would be to handle the flat iron properly and respect the recommendations. Unfortunately, that is not always the case. A study showed (Hahn et al, 2015) that manufacturers of high priced flat irons provided their customers with more detail regarding the temperature recommendations, for example, by recommended thermal hair care products. Unfortunately only one of the analysed manufacturers provided information about the importance of dry hair during hair straightening. But there was no information about heat damage and overall information lacked entirely when it came to low cost hair straighteners. This only means that customers who cannot afford more expensive hair straighteners will be more prone to hair damage due to the lack of information provided.

How to Avoid Heat Damage When Straightening Hair

Pre-treatment seems to be one of the measures proposed by most studies and experts. Pre-treatment of hair with selected polymers will provide thermal protection to the hair surface and the cortex which is usually damaged during flat ironing. Even more, pre-treatment of hair will also reduce hair breakage during combing and improve the restoration of water content inside the thermally treated hair (Zhou et al, 2011). However, once the damage is done, there is little to do for the structure of hair. A study shows that thermal damage to hair is irreversible even after mild degradation so it’s important to make sure that we prevent these problems as much as we can. (Jachowicz, 1987)
Overuse of the flat iron is another way to avoid heat damage. Overuse doesn’t only refer to the number of straightening sessions you are doing per week, but also to the amount of times you are passing the flat iron over a strain of hair. If you can, avoid repeating this too many times, as it may prove to be detrimental to its structure; unless you have extremely curly hair you will only need to use the iron a couple of times over the same strain of hair. Many people also make the mistake of holding the iron for a long time on a strain of hair while also pressing too hard on it. This can be extremely detrimental — the movement has to be quick, lightly pressed and in one direction, otherwise you may easily scorch your hair. Here’s how the experts do it:
Avoiding steam damage is essential and while you might not see the results immediately, you will certainly notice split ends after styling your hair this way for a couple of times. This is because wet hair is a lot more elastic but it can also break while applying tension on it which leads to split ends and broken strands. So, dry your hair properly before starting to style it with a flat iron.


Although the general consensus is that excessive heat causes damage to hair, using a hair straightener doesn’t have to be harmful for your hair as long as you take some precautions and don’t overuse it. Using heat protective treatment, avoiding straightening your hair while it’s wet and never going over 157 Celsius will guarantee smooth hair without the split ends or burned hair.

References and further reading