Heat is one of the most common and most underestimated causes of hair damage. Anyone who styles regularly will be affected, whether their hair is coloured or not. Breakage, dullness, split ends and a gradual loss of natural body and shine can be signs that heat is taking its toll. If you want to protect your hair from heat, it begins with understanding exactly what happens every time a styling tool touches your hair.

We know how significantly heat affects hair, which is why we decided to show it. Our Instagram reel comparing two straighteners running at different temperatures reached 13.5 million views. The response was extraordinary. Here is what is really going on every time heat meets hair.

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What heat actually does to your hair

Applying heat to hair triggers two distinct types of damage that build on each other over time.

The first is structural. Elevated temperatures alter the keratin proteins responsible for your hair's strength, elasticity and shape. Repeated heat stress weakens the hair shaft, leading to dryness, increased breakage, split ends that travel further up the hair and a progressive loss of natural shine and body. This is true for all hair types, not just those that are colour-treated or chemically processed.

The second is surface damage. Heat forces the hair cuticle, the outer protective layer, to lift open. When the cuticle lies flat and smooth, it gives hair its shine and helps it hold onto moisture. Repeated lifting without full recovery leaves hair porous, frizzy and difficult to manage. Colour-treated hair loses vibrancy more quickly too, because open cuticles cannot hold onto pigment.

We cover this in more detail in our guide to caring for damaged hair. The core principle is straightforward: the higher the temperature of your styling tools, the more aggressively both forms of damage occur. Choosing the best straighteners and dryers is not an indulgence. It is one of the most practical decisions you can make for the long-term condition of your hair.

The science behind 185°C

Research published in the Journal of Cosmetology and Trichology found that hair straightened at 185°C maintained its structural integrity, while hair treated at 220°C showed irreversible cortex damage and significantly increased breakage.

At 185°C, hair enters what researchers describe as the glass transition phase: it becomes pliable enough to hold a style, then sets as it cools, without causing damage to the cortex or cuticle in the process.

GHD's research and development team in Cambridge arrived at the same conclusion independently. Style above 185°C and you risk permanent damage to the hair's internal structure. Style below it and the result will not hold, which leads to more passes with the tool and greater cumulative heat exposure overall.

185°C is not a number chosen for marketing purposes. It comes from rigorous material science research and sits at the foundation of what the best straighteners on the market are built around. It is also the temperature at which we work in the salon when using heat styling tools on clients.

Why this matters for coloured hair specifically

Colour-treated hair is more porous than natural hair. The colouring process opens the cuticle to allow pigment to be deposited, and even with thorough aftercare, that porosity increases over time. A more porous cuticle lifts more readily under heat, meaning colour molecules escape sooner and vibrancy fades faster than it should.

If your colour looks beautiful when you leave the salon but loses its depth within a few weeks, your styling tools at home are likely contributing to that. Read more about why colour fades and what you can do to slow it down in our colour fading article.

Knowing how to protect your hair from heat is especially important after investing in colour, but the structural benefits of lower, consistent temperatures apply to every hair type.

Why most tools are working against you

Many straighteners on the market operate between 200°C and 230°C. Some go higher. The damage this causes builds gradually and is often not noticeable until it becomes significant. Hair becomes progressively drier, more prone to breakage, harder to style well and lacking the shine and volume it once had.

Our Instagram reel demonstrated this directly. We held two different straighteners on coloured hair for ten seconds each. The difference in colour loss and visible structural damage was clear and immediate. The GHD Platinum Plus, running at a consistent 185°C, caused none of the damage visible on the hair treated with the higher-temperature tool.

This is why we are precise about what we recommend and why the tools you use at home every day have a far greater impact than most people realise.

Why we recommend GHD

We use GHD tools in the salon because of the science behind them, not simply brand preference.

The GHD Platinum Plus straightener uses ultra-zone predictive technology that monitors temperature 250 times per second, adjusting across both plates to hold a consistent 185°C regardless of hair thickness or the speed at which you style. That level of consistency throughout every stroke is something most tools on the market cannot deliver. The difference is visible not just in a single session but in the overall condition of your hair over months and years.

The GHD hair dryer applies the same thinking to blow-drying: controlled, consistent heat that dries the hair efficiently without placing unnecessary thermal stress on the shaft. For those who curl, the GHD Curve tong range produces defined, long-lasting results at the same carefully maintained temperature.

Investing in a quality GHD hair dryer and GHD Platinum Plus straightener is one of the most effective ways to protect your hair from heat damage over time and to maintain its health between salon appointments.

If you style regularly, these are the tools that allow you to do so without the slow, cumulative cost to your hair's condition. They are our recommendation for the best straighteners and dryers for anyone who wants results without compromise.

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Heat protectant is not optional

We put this to the test in another experiment, which you can see in our Instagram reel. We applied IN's Good Hair Guardian Thermal Primer to one half of a slice of bread, left the other half unprotected and placed both in a hot oven. The unprotected side burned. The protected side showed almost no change.

It is a straightforward demonstration, but it illustrates precisely what the best heat protectant spray does. It creates a barrier between the styling tool and the hair shaft. Without it, even a GHD Platinum Plus is working harder than it needs to, and your hair is absorbing more direct heat as a result.

IN's Good Hair Guardian Thermal Primer is our recommendation for most hair types as the best heat protectant spray for everyday use. It protects against temperatures up to 400°C, detangles, reduces frizz and adds shine with a weightless finish that will not leave hair heavy or coated. Apply it to damp hair before you begin styling, comb through from root to ends and pay particular attention to the tips, which are the oldest and most fragile part of the shaft.

The key principle is simple: use a heat protectant spray every single time you style.

The right brush makes a difference too

The brush you use during blow-drying affects how much tension and heat exposure your hair experiences throughout the process. The Fromm Elite Thermal Brushes are designed to work with heat rather than trap it, giving you a smoother, more controlled finish at home without additional passes or unnecessary stress on the hair.

Watch your water temperature

Heat styling tools attract most of the attention when it comes to thermal damage, but the temperature of the water you wash your hair with is a factor too. Hot water opens the hair cuticle in the same way that styling tools do, stripping moisture and making it harder for hair to retain condition and shine over time.

Washing with lukewarm water and finishing with a brief cool rinse encourages the cuticle to lie flat, which seals in moisture and leaves hair looking smoother and healthier. It is a small adjustment that makes a consistent difference.

Protecting your hair from heat is a long-term habit

Healthy hair comes from consistent, considered decisions made over time. The tools you choose, the heat protectant spray you apply, the temperature of your shower water, the way you dry and style: none of these individually is dramatic, but together they make a genuine and lasting difference to how your hair looks, feels and behaves.

Good tools, thorough preparation and reliable protection work together to keep breakage down, split ends in check and the kind of shine and body that signals genuinely well-maintained hair.

If you would like personalised advice on how to protect your hair from heat and the right routine and tools for your hair type, we would be glad to help. Book a free consultation and we will put together a home care approach built around your hair, your lifestyle and your goals.