Can a Hair Dryer Damage Your Hair?

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Hair dryers dry your hair by blowing a stream of hot air through a diffuser right onto your moist hair, thus speeding up the evaporation. Though it seems harmless, the damage the hot air does to the hair is often one of the most overlooked effects of a hair dryer. Let’s take a quick look at what hair dryers do to your hair.

The science of hair drying, hair, and rapid moisture loss

When you turn on the hair dryer, the electricity powers the heating element (usually ceramic) and a motor (attached to a fan) behind it. The fan pushes out the hot air through the diffuser right onto your hair. In other words, a hair dryer forces convection.

Let’s take a look at the hair shaft.

It consists of several layers as shown in this illustration. The outermost layer is the cuticle and the innermost layer is the medulla. The cortex is one of the inner layers between the cuticle and the medulla. It is the thickest part of the hair and has most of the melanin content. In other words, the cortex is responsible for the stiffness and colour of your hair.

The hair fibre contains moisture at different levels, and when the heat is applied, the moisture evaporates at different rates. But the problem is, that the applied heat is instantaneous and drastic and it interacts with just the surface of the hair more. The hair undergoes a rapid moisture loss on the surface. With rapid moisture loss comes rapid and uneven shrinkage in the size of the outer layer. As soon as the outer layer shrinks, there’s a mini tug-of-war between it and the inner layer (which is still moist and refusing to shrink instantly), causing it to break or split. This type of forced evaporation makes the hair brittle and causes stresses through the layers, from the cortex to the cuticle, creating cracks in the fibre.^[1]

In the linked study, cuticle damage has been observed significantly in people who used hair dryers in their grooming routine.

Conclusion

Yes, using a hair dryer can damage your hair. Any thermal action forced onto your hair will subject the hair to lose moisture and shrink rapidly and cause breakage and splits. So, apart from hair dryers, other cosmetic styling devices like curling tongs could damage your hair and cause conditions like bubble hair and hair fibre buckling.^[1][2]

Footnotes

1. Gamez-Garcia, Manuel. (1998). The cracking of human hair cuticles by cyclical thermal stresses. Journal of Cosmetic Science. 49. 141-153.
2. GUMMER, C. (1994). Bubble hair: a cosmetic abnormality caused by brief, focal heating of damp hair fibres. British Journal Of Dermatology, 131(6), 901-903. doi: 10.1111/j.1365-2133.1994.tb08599.x
3. Savitha, A., Revathy, T., & Sacchidanand, S. (2011). Bubble hair and other acquired hair shaft anomalies due to hot ironing on wet hair. International Journal Of Trichology, 3(2), 118. doi: 10.4103/0974-7753.90832
4. Ruetsch, S., & Kamath, Y. (2004). Effects of thermal treatments with a curling iron on hair fiber. International Journal Of Cosmetic Science, 26(4), 217-217. doi: 10.1111/j.0142-5463.2004.00223_2.x