brunette with wet hair pointing at hairdryer

Heat damaged hair? Here’s everything you need to know

It’s time to beat heat damage hair!

Heat damaged hair is a term thrown around a lot these days. Like other common hair issues, you probably have an inkling of it is, but do you know what causes heat damaged hair?

On a basic level, heat damage is caused by styling tools such as straighteners, curling tongs and hairdryers. With regular use of these tools, your delicate strands can become dry, brittle and split, which leaves your hair looking and feeling rough (urgh!).

Now, while this all seems fairly straightforward, there’s more to this story. To break this down and enlighten you to the hard truths of heat damage, we’ve enlisted the help of some hair experts who will shed some light on it for us.

What causes heat damaged hair:

  • High temperatures which can break the inner protein bond of the hair fibre
  • Heated styling: using tools such as straighteners, curling tongs and hairdryers (yes, really!)
  • The sun, because like skin, hair can be damaged by the extended sun exposure

What is heat damage?

Heat damage hair: Young woman with reddish brown shoulder length wet hair pointing to a hairdryer
Did you know that even hairdryers can cause heat damage? Credit: Verity Jane Smith

As we said, heat damage primarily occurs through the use of heated styling tools, but just how do these everyday stylers affect our hair?

To give you a more detailed explanation, we sat down with Peter Bailey, Global Technical Manager, Hair Care at Unilever, who told us that “the damage sustained by hair due to blow drying is primarily surface damage, [whereas] when straightening irons are used at high temperatures the damage to the hair fibre is internal.”

Heat damaged hair before and after: Back view of hair without and with heat protectant
Heat protectant is a must if your styling with heat (heat damaged hair before and after). Credit: Verity Jane Smith

Heat damaged hair: Before and after

He went on to explain that while blow-drying, the temperature sits at around 50°C and increases the fibre-to-fibre contact, which can lead to cuticle chipping and leave the surface of the hair fibre feeling rough. Straightening and other styling irons, on the other hand, are much hotter and at around 150°C the hair protein in the cortex undergoes a transition where the heat energy can break some of the inter protein bonds that give the hair fibre is strength and structure.

What does all this mean for your hair? It becomes dry, brittle, and split (AKA damaged), and leading you to have a bad hair day! But there is one other type of heat damage you should watch out for, too…

A young brunette girl with short hair wearing a patterned dress with her hands in/and on her hair
Can you actually sun damage your hair? Credit: Verity Jane Smith

Can too much sun damage your hair?

Ever noticed that after a two-week holiday on the beach your strands feel less than silky? That’s because just like skin, your hair can also become sun damaged.

Peter explains that over long periods of UV light exposure, “the creation of highly reactive free radicals can react with the amino acids within the hair protein chains” which can lead to the protein structures unfolding, resulting in hair that is weaker and prone to damage.

Long-term exposure to UV light can also contribute towards the removal of the lipid layer on the outer surface of the hair fibre, making it rougher and less easy to comb/detangle. We know, scary stuff, right?

Sun-damaged hair symptoms

  • Colour change
  • Reduced softness and gloss
  • More split ends

So, with that said and done, how can you tell if your hair is suffering from sun damage? Like damage done to skin, there are some visible changes. UV damage is perceived through colour change, reduced softness and gloss, and more split ends.

How can protect my hair from sun damage?

  • Cover up using a hat
  • Use hair products with UV filters
  • Limit direct sun exposure

We’re not going to tell you to stay indoors all summer long, so you’re probably wondering how to protect against sun damage, right? Well, the best way to do this is to cover up with a hat, but if you really feel the urge to show off your locks, you can try using the VO5 Firm Hold Hairspray that is formulated with UV filters to help protect against UV damage.

Close-up of a woman holding the TRESemmé Biotin + Repair 7 Primer Protection Spray
Avoid heat damaged hair by using a heat protectant. Credit: Verity Jane Smith

Tips for avoiding heat damaged hair

  • Reduce heated styling
  • Turn down the temperature of your hair styling tools
  • Use a heat protectant

Now that you know the potential damage you’re doing to your precious strands, we hope you’re ready to revise your hair care routine – and it’s actually really simple.

To stop heat damage from occurring, all you have to do is… stop using heat. We told you it was simple! But we know that this isn’t possible for some of your styling addicts out there, so instead of going cold-turkey, you can send your hair to rehab by turning down the temperature of your heated appliances.


Even if you do lower the temperature of your styling tools, you should still use a heat protectant. Heat protectants act as heat sinks and stop the heat from penetrating deep into the hair fibre structure. Less heat = less damage.

How to repair heat damaged hair

heat damaged hair tips: black woman lying on a silk pillow
Why not try a silk pillowcase?

If you feel you’re already suffering from the effects of heat damaged hair, then there are some things you can do to remedy this. The most important one to remember is to always use a heat protectant before applying heat to your hair in the future, but for now, try one of these top tips:

Tip 1: Chop off your split ends

Unfortunately, once your hair has been damaged and split ends have occurred, there isn’t anything you can do to repair them. Your only option is to chop them off, and give your hair a fresh, new start.

We know that this may seem daunting, but don’t fret: if you regularly trim your hair, it will keep it looking healthy, and help you retain a longer length, too!


Tip 2: Use a weekly deep conditioning treatment

Like we said, you can’t actually repair heat damaged hair, but you can help moisturise rough strands by using a weekly deep conditioning treatment.

These treatments come in all shapes and sizes, but we especially love nourishing hair masks (like the TRESemmé Biotin +Repair 7 Intensive Mask) as these really do pack a punch in the hydration department!

Tip 3: Go heat-free

This goes without saying: if your heated styling tools are causing too much damage to your strands, then you’ll need to give them up for a while!

Try air-drying your hair instead of blow-drying it or using a heatless curling method instead of picking up the curling tong – you just need to think outside of the box.

Tip 4: Sleep on a satin or silk pillowcase

If your tresses are already damaged from the use of heated styling tools, you’ll also want to limit any other forms of damage, too. Something many people don’t know is that when you sleep on a cotton pillowcase, your strands rub together, causing friction and resulting in more damage (eek!).

However, when you sleep on a silk or satin pillow, both the amount of friction created and moisture absorbed from your strands will be reduced. Sweet dreams!


And there you have it, folks! From now on make sure you’re properly protecting your strands from heat and never have a bad hair day ever again.



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