It isn’t news that applying heat to hair is damaging, but it’s kind of like knowing that an afternoon coffee will keep you up late — it may not be good for you, but you still have to have it. The difference, though, is that there is something you can do to reduce damage the next time you pick up your curling iron or hair dryer: apply a heat protectant spray.
There are plenty of products that boast heat-protecting benefits, but they can raise more questions than answers. Is heat protectant really necessary? And does heat protectant actually work? We’re here to clear up the confusion and to explain the science behind heat protectant spray. Once you understand how this powerful product works, you’ll reach for it more — and your hair will thank you.
Key Takeaways
-
Heat protectant measurably reduces thermal and friction damage, but spacing out heat styling + using lower temperatures are still important for healthy hair.
-
Dry hair begins to denature [or weaken] at 446°F [230°C] + wet hair at 302°F [150°C], yet many hot tools reach 400°F to 450°F [204°C to 232°C].
-
A thin, flexible film seals the cuticle, slows moisture loss, adds slip to reduce friction + distributes heat evenly to prevent hot spots.
-
Common ingredients include film-forming polymers, silicones, lipids + oils, and proteins + peptides, with antioxidants in some formulas.
-
Regular use means fewer split ends + less breakage, softer + more flexible strands, and a smoother, shinier finish with fewer styling passes.
-
The right formula depends on your hair type, texture, styling frequency, wet or dry application, tool type + temperature settings.
Why is heat damaging to hair?
Dry hair starts to denature — meaning it begins to structurally break down — when exposed to temperatures of 446°F (230°F) or higher. Wet hair is even more vulnerable, with denaturation starting at 302°F (150°C). That’s pretty alarming, considering that many hot tools, including curling wands, flat irons, and hair dryers easily exceed the 400°F (204°C) mark, with some even going all the way up to 450°F (232°C).
To understand what this means and why it happens, we must first understand the anatomy of hair.
Each strand of hair is composed of three main layers:
-
The medulla, which provides structural reinforcement
-
The cortex, which gives hair its strength
-
The cuticle, the outer layer of the hair shaft that protects the cortex
The cuticle is also coated with a lipid layer, known as the F-layer, which gives hair its smooth, soft look and feel.
Both the inner cortex and the cuticle primarily consist of keratin, a strong, fibrous protein. Heat makes keratin more pliable, which is why hot tools are used to achieve smooth styles. However; when keratin is subjected to repeated high heat stress, its structure can denature and lose strength and elasticity. At very high temperatures, heat can break the strong disulfide bonds that hold keratin chains together.
The more heat you apply [and the higher the heat setting], the more damage you expose your strands to. As proteins denature and bonds disrupt, the cuticle layer lifts, creating an uneven, coarse texture. This also exposes the inner cortex, which rapidly loses moisture and begins to break down. The final result is hair that looks dry, feels brittle, and is vulnerable to breakage.
What is heat protectant?
You know that heat is harmful to hair, but avoiding it entirely is easier said than done. Whether you need a smooth finish for a big event, don’t have the time to sit around waiting for your hair to air-dry, or simply prefer the look of a blow-out, odds are you’re going to pick up a hot tool at some point. What matters most is protecting your hair before you apply heat, which is where heat protectant comes in.
Heat protectant is exactly what it sounds like: a pre-styling product you apply before using hot tools to shield your strands from the stress of heat and slow moisture loss. Think of it the same way you would apply sunscreen before a day at the beach. Heat protectants and can take many different forms, including oils, mousses, and serums, though by far the most popular heat protectant products are sprays. Many heat protectant products also offer multiple benefits, such as smoothness, frizz control, detangling, and volume.
How does heat protectant work?
Not all heat protectants are the same, but, generally speaking, they apply a thin, flexible barrier around each strand that helps seal the cuticle and reduce moisture evaporation . This barrier, or film, also slows down the heat penetration into hair fiber and distributes heat more evenly along the hair’s surface, preventing hot spots from forming. By smoothing and sealing the cuticle, it also lessens friction from styling tools. While they can’t make hair heat-proof, heat protectant sprays, oils, and serums do preserve keratin structure and cuticle integrity, dramatically reducing the amount of structural and mechanical damage caused by flat irons and other hot tools.
What is in heat protectant?
Most heat protectants rely on a similar set of ingredients, even if the exact formulas vary from brand to brand. These include:
-
Film-forming polymers that apply a thin, protective coating along strands to reduce friction and mechanical abrasion and stabilize keratin during heating
-
Silicones, which form a hydrophobic, lubricating film that protects against thermal and UV damage
-
Lipids and oils, which increases “slip” for lower cuticle abrasion and makes products easier to apply evenly across strands
-
Proteins and peptides that bind to hair, reinforce keratin, and enhance thermal stability
Some heat protectants also include antioxidants and vitamins to limit oxidative damage from heat and UV rays.
Living Proof’s Perfect hair Day™Heat Styling Spray, which offers heat protection up to 450°F/230°C, uses our patented Healthy Hair Molecule to polish and protect strands while blocking humidity and a lightweight emollient blend to smooth hair and enhance shine. Its cationic blend controls static by conditioning hair and smoothing the cuticles. The positively charged particles in this blend naturally bind to the negatively charged particles in hair strands like a magnet, making this lightweight spray effective on both damp and dry hair.
Be honest: does heat protectant actually work?
The simple answer is “Yes, heat protectant actually works.” The more nuanced answer is “Yes, heat protectant actually works, but you need to have realistic expectations for it.”
No matter which brand or formulation you use, heat protectant isn’t a silver bullet that will make your hair impervious to heat damage. Using hot tools on a daily or even weekly basis — especially if you crank up the temperature — will inevitably damage your strands. But, if you space out heat treatments, consistently apply protectant beforehand, and try to use lower-temperature settings, you can drastically reduce the amount of thermal damage you do to your hair, keeping strands softer, smoother, and healthier-looking.
What are the benefits to using heat protectant on your hair?
Adding a heat protectant to your haircare routine is a simple adjustment that can have a major impact. Here are just a few of the benefits you’ll see with regular use:
-
Fewer split ends and less breakage: When you apply heat to your hair, it can lift the overlapping scales that make up the cuticle layer. When those raised scales are subjected to additional thermal or mechanical stress — for example, repeatedly sliding a hot plate over strands or brushing your hair — it causes further damage. By smoothing the cuticle layer and adding slip to strands, heat protectants reduce friction, which prevents breakage and helps hair look healthier for longer.
-
Less dry, stiff hair: We’ve all seen (or maybe experienced) it before: strands that have sustained so much heat damage that they look fried and straw-like. This happens because hair loses water quickly when exposed to high temperatures, and rapid water loss makes the hair fiber less flexible. Heat protectants can slow moisture loss and help the cuticle lie flat, giving it a more smooth, supple feel.
-
Smoother, shinier finish: When the scales of the cuticle layer lie flat, it creates a smooth surface that reflects light more evenly and makes hair look glossier. This same smoothing effect can also reduce frizz and flyaways, in part because smoother strands are less likely to snag on each other and can be more resistant to the effects of humidity. For many people, that means a sleeker blowout or more even results with fewer passes, which is a major win because total exposure is one of the main drivers of damage.
If you use hot tools on the regular, heat protectant could be your new best friend. Combine with damaged hair repair products specifically formulated for heat-damaged strands to give your hair the extra strength and nourishment it needs.
How do you choose the right heat protectant?
When shopping for heat protectant spray or other products with built-in heat protection, consider the following:
-
What is your hair type — fine or thick?
-
What is your hair texture — straight, wavy, curly, or coily?
-
How often do you apply heat to your hair?
-
Do you usually apply heat to wet or dry hair?
-
What types of hot tools do you use?
-
How high do you set the temperature on your hot tools?
Each of these factors will help you determine which formula is right for you. After all, any sort of pre-heat styling product should help you achieve your ideal style, not weigh your strands down.
Looking for tips on how to choose the right heat protectant for your hair type and texture and how to apply it? Check out our blog post on the subject — plus, get a customized product lineup, including heat protectant, when you take our free haircare quiz.
