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Hair Hot Iron Damage: Which products really work?

Heat styling is the most popular way to straighten and shape your hair. Unfortunately, it can also be very bad for you. This article explains why high temperature styling is bad for hair and tells you where to buy products with the best ingredients to protect your hair from heat.

Why heat is bad for hair?

Heat exposure causes three types of hair damage: 1) decomposition of hair pigment (melanin) which cause changes in hair coloration; 2) damage to the fiber surface which makes the hair feel rough and look dull, and 3) weakening of internal hair proteins which can result in increased breakage. These effects are greatest when hair is exposed to temperatures above 130C. Blow dryers, curling, and flat irons are all capable of inflicting significant heat damage.

How do heat protection products work?

No one knows for sure, but here are three possible theories to explain how heat protection products work:

Uniform heat distribution

Products that leave a “buffering” layer on hair can prevent direct contact between the heating appliance and the hair surface. This protective layer can help minimize local overheating effects.

Reduced heat conduction

Almost any product that makes the hair more slippery can claim heat protection because if the flat iron or curling iron slides through the hair more quickly there is less likelihood of damage. This effect can reduce heat conduction and therefore decrease damage.


At least one study suggests that the thermal decomposition of hair protein is caused by an oxidation reaction. Since oxidation and reduction are opposite chemical reactions, a reducing chemical like sodium bisulfite or ascorbic acid may stop the damaging reaction.

How is heat protection measured?

Heat protection can be measured using a variety of experimental techniques. Three common methods are: 1) Combing analysis to measure increases or decreases in hair surface roughness, 2) Fluorescence spectroscopy to analyze the breakdown of hair protein (usually tryptophan), and 3) Texture analysis to show changes in the mechanical properties of hair tresses.

(Reference: J. Cosmet. Sci., 49, 245-256 (July/August 1998) Thermal degradation of hair. II. Effect of selected polymers and surfactants R. McMULLEN and J. JACHOWICZ, InternationalSpecialty Products,Wayne, NJ 07470.)

Which ingredients really work?

There are dozens (hundreds? thousands?) of products that claim to protect hair from heat damage. Do they really work? The scientific literature shows only a few chemical compounds that have been studied and shown to provide a real, measurable benefit. For best results, look for leave-in treatment products that have these ingredients in listed toward the top of the ingredient list (in the first 5 ingredients, or so):

  • PVP/DMAPA acrylates copolymer
  • Hydrolyzed wheat protein
  • Quaternium 70

(This doesn’t mean these are the ONLY ingredients in the universe that really work, but these are the only ones that have published data. Strong reducing ingredients that work by the oxidation-prevention mechanism described above are not recommended because they may cause other types of hair damage.)

What about “heat activated?”

One final note: be careful not to confuse “heat protection” with “heat activation.” Activation simply means the product undergoes some kind of change when heat is applied. Typically this refers to setting agents (in technical jargon, thermoplastic resins) which melt at the temperature of blow dryers or irons, and therefore form tighter bonds with the hair.

What Products Should You Buy?

If you’re looking for a hair protectant that contains ingredients that really work, click here to buy Ouidad Climate Control Heat & Humidity Gel; it contains 2 of the 3 proven ingredients.


Not interested in buying a product now but you want to learn more about products that really work? Download our FREE guide on How To Save Money on Beauty Products.

Comments on this entry are closed.

  • Berryb April 22, 2015, 7:28 am

    Does the kevin murphy damage defence spray really provide “unrivalled protection”? It includes the Kevin Murphy complex which they claim is more effective than traditional copolymers

    • Randy Schueller April 22, 2015, 7:52 am

      They named a complex after a person? Weird. “Unrivaled protection” means it works at least as well as anything else on the market. That claim would have been very difficult and costly to substantiate so I’m assuming they mean it as puffery.

  • Alessandra October 13, 2015, 1:45 pm

    Hi there, I’m glad that someone actually spelled out what ingredients to look for! However, I am having trouble finding a product light enough for baby fine strands and yet effective. I don’t iron my hair but blow dry it with a round ceramic brush, and it seems enough to fry my delicate ends. I checked many products and many have good ingredients, but also contain drying denaturated alcohol (John Frieda Heat Defeat), or greasy/heavy dimethicone as the 2nd or third ingredient (Tresemme heat tamer). Others, including from high end brands, do not list any of the ingredients you recommend (Philip Kingsley Daily Damage Defense and Tricho Pro, Evolvh SmartStart, Marula daily moisture conditioning heat protector, Shu Uemura Wonder worker). Lastly, I found two products that claim to both style/volumize AND protect from heat (which sounds easier than layering heat protectant and mousse), but will they really protect: Tressemme Thermal Creations mousse and Kerastase Volumifique Spray Expanseur…. But are they effective? Only the kerastase spray has at least the acrylates copolymer, and quaternium 80 (but not 70). In short, I can’t find a product that fits your description and recommended for fine hair (possibly a volumizing mousse, I love the way they make my hair feel)

  • Zlatka January 18, 2016, 4:36 am

    Syoss Heat Protection Spray has wheat protein in it and it’s not expensive, but unfortunately, it also contains a lot of alcohol.

  • Joy March 2, 2016, 10:12 am

    From a damage-reducing perspective, what is your opinion of the different materials used in heat-based styling tools? Different companies always tout the benefits of tourmaline/ceramic/gold-plated/etc.

    • Randy Schueller March 2, 2016, 7:35 pm

      I haven’t seen data that indicates that there’s any difference between the different materials.

      • Joy March 8, 2016, 10:53 am

        Interesting, thank you.

  • Stephanie March 28, 2016, 2:50 pm

    I have been using the karmin Spray Heat Protector and works really well for my hair

  • Christy July 14, 2016, 8:28 am

    The Spray Heat Protector by karmin is my favorite, makes my hair look so healthy. =D

  • Jereece McKee July 20, 2016, 9:10 pm

    Regarding using a flat iron on wet/damp hair: Please don’t do this! Make sure the hair is completely dry before using a flat iron. Also, make sure to use only medium heat with the blow dryer and the lowest heat setting on the flat iron that still smooths the hair. Less heat, fewer & slower passes of the iron down the length of hair is recommended. Especially with curly hair, hot air from the blow dryer can cause more frizz. And too much heat is more damaging to hair, especially with repeated use.
    Thanks for all the good research guys!

  • Emma December 1, 2016, 1:28 pm

    I’m not an expert, however…

    There is only one study referenced in this article, from 1998 (18 years ago). It’s here http://journal.scconline.org/pdf/cc1998/cc049n04/p00245-p00256.pdf

    Looking at the study, it would seem that the data in the graphs does not lead to a clear conclusion that these ingredients work. Error bars overlap and in several tests these treatments come out much worse than untreated hair (especially the hydrolyzed wheat protein). Patterns are far from clear. I’ve made a brief attempt to find more recent or conclusive studies but failed.

    It’s incredible, given the amount of money spent on these products that it doesn’t seem to be worth anyone’s while to test them. I guess that’s because most people are convinced by “scientific” claims in adverts without needing to see data. Shouldn’t someone be regulating statements made and publishing comparisons? A consumer organisation perhaps? Without data this is just fiction.

    • Randy Schueller December 2, 2016, 8:32 am

      In an ideal world it would be wonderful to have every statement tested and confirmed. But there are tens of thousands of cosmetic products (and new ones created all the time.) It would be a daunting (and expensive!) task for a consumer organization or anyone else to try and validate it all. Who’s going to pay for that? No one!

  • Edith December 2, 2016, 10:19 am

    Best I have ever used is the Karmin Spray Heat Protector 😉

  • Maria May 4, 2017, 3:24 pm

    Hi, thanks for all this helpful info!

    Please could you share your opinion on silicone as a heat protectant?