Heat and hair: what flat irons and blow dryers do to your hair (and how to protect it without silicones)

The flat iron at 230 °C. The hairdryer at maximum power. The curling iron three times over the same strand. We do it almost without thinking, and our hair pays the price. But the solution isn't to give up heat — it's to understand what happens and protect yourself smartly.

At Ryōho Cosmetics, we formulate without silicones, which means we can't hide damage under a layer of plastic. We have to genuinely prevent it. Here's how.

What happens to hair when you apply heat?

Hair is primarily composed of keratin, a protein structured in chains held together by hydrogen bonds and disulfide bridges. Heat temporarily breaks these bonds — which is why you can straighten or curl hair with temperature.

The problem is that excessive heat doesn't just break temporary bonds; it also:

• Irreversibly denatures keratin, weakening the hair fiber
• Evaporates the internal water from the hair, leaving it dry and brittle
• Damages the cuticle — the protective outer layer — causing hair to lose shine and become frizzier
• Oxidizes hair lipids, accelerating fiber aging

And all this occurs at temperatures above 150 °C. Most home flat irons operate between 180 and 230 °C.

The myth of silicones as protection

The conventional cosmetic industry solves this problem with silicones: they create a layer over the cuticle that acts as a thermal barrier and gives a feeling of softness and shine. It works in the short term, but it comes at a cost:

• Silicones accumulate in the hair with continued use, dulling the hair and hindering the penetration of other active ingredients
• They require harsh sulfates to be removed — which damages the hair microbiome
• They don't repair damage: they hide it
• Most are not biodegradable

At Ryōho, we choose not to use silicones. This forces us to work with ingredients that genuinely protect and repair the hair fiber from within.

Silicone-free heat protection: what to look for

There are plant-based alternatives with proven efficacy in protecting hair from heat:

• Hydrolyzed proteins (from wheat, silk, or rice): penetrate the hair fiber and strengthen keratin from within, reducing breakage due to heat
• Vegetable oils with a high smoke point (argan, marula, baobab): form a natural barrier over the cuticle without occluding it, providing flexibility and resistance
• Panthenol (provitamin B5): deeply hydrates and improves hair elasticity, reducing breakage
• Vegetable ceramides: repair cuticle cracks and seal in internal moisture

5 habits to reduce thermal damage starting today

1. Always dry to 80% before using a flat iron. Applying heat to damp hair is especially destructive: the internal water boils and breaks the fiber from within.
2. Lower the temperature. For most hair types, 160–180 °C is sufficient. Reserve high temperatures for very thick or resistant hair.
3. One pass, not three. Each additional pass multiplies the accumulated damage. If you need more than two passes, the problem is preparation, not temperature.
4. Apply protector before, not after. Heat protectant should be on the hair before heat is applied, not as a finishing product.
5. Alternate with heat-free days. Hair needs time to recover its natural hydration. Heat-free days are just as important as protection when you do use heat tools.

The foundation is everything

The best heat protection starts in the shower. Well-nourished hair, with a sealed cuticle and a balanced scalp microbiome, resists the stress of heat much better than hair weakened by harsh products.

Start with our Shampoo with Prebiotics: it cleanses gently and prepares the hair fiber in optimal conditions. Complete the routine with our Keratin Leave-in Conditioner — ideal for sealing the cuticle and providing extra protection before heat styling — or with the Volumizing Conditioner with Keratin if you're looking for body and resilience without weighing hair down.

Hair care isn't complicated. It's about understanding what it needs and giving it to it.