What is the difference between hair dryers that cost dozens, hundreds, or thousands?

If you go to an online store to buy "hair dryers" and do a quick search, you will find that their prices range from a few dozen yuan to several thousand yuan.

I clearly wanted to buy a tool to dry my hair, but the promotion of the hair dryer was confusing. It said "hurricane-level wind", "negative ion care", and "moisturizing and caring for hair". These promotions made me feel like I wanted to blow dry my hair even after washing it.

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Do hair dryers really have so many magical effects? What is the difference between a hair dryer that costs dozens of dollars and one that costs thousands of dollars? To understand this, we must first talk about the structure of a hair dryer.

The structure of the hair dryer is very simple

As early as the end of the 19th century, the earliest "hair dryers" were born, but early hair dryers were very large and needed to be used in barber shops.

An early hair dryer used in a barber shop. Image source: Wikipedia

Handheld household hair dryers began to appear in the early 20th century, and the first patent for a hair dryer was issued in 1911.

Although the hair dryers at that time were rather crude (as shown below), there was a fan at the back of the hair dryer. The air would pass through the heating tube in front and then blow out hot air, which could be used to dry the hair.

1911 Hair Dryer Patent, Image Source: Patent US994259A

Over the past 100 years, the appearance of hair dryers has changed a lot, but these two modules have not changed. The "blowing module" and "heating module" are still the two most important modules in a hair dryer. A hair dryer with negative ion function adds a negative ion generator to these two modules.

Since the core components are similar, why do the prices of hair dryers vary by hundreds of times? What parameters should we pay attention to when choosing and using a hair dryer?

In fact, the most relevant parameters for hair dryers are nothing more than temperature, wind speed, noise and negative ions. Let's talk about them one by one.

temperature

First, let’s talk about temperature.

The essence of using a hair dryer to dry hair is to use wind and heat to accelerate the evaporation of moisture from the hair. The evaporation rate of moisture is directly proportional to the temperature and wind speed.

Theoretically, the higher the temperature, the faster the hair will dry, but in reality, the higher the temperature of the hair dryer is not necessarily better.

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Some people believe that using a hair dryer will damage hair. This statement makes sense, and the "culprit" behind the damage to hair is high temperature.

A study in 2011 compared the damage to hair caused by different hair dryer temperatures. The results showed that the higher the temperature when blowing hair, the more severe the damage to the hair cuticle. For example, in the figure below, A is the control group, B is the natural air drying group, C is blow-dried at 47 degrees Celsius, D is blow-dried at 61 degrees Celsius, and E is blow-dried at 95 degrees Celsius.

If we compare the CDE images, we can see that as the temperature rises, the cracks and holes on the scales on the surface of the stratum corneum increase. Moreover, when treated at 95 degrees Celsius, perforations appeared on the outermost side of the stratum corneum.

The condition of the cuticle on the hair surface after different treatments. Image source: Reference 2

Therefore, this study recommends that it is best to use lower temperatures when blow-drying your hair.

Of course, there is another point worth noting in this study. Among the several treatments, the cracks and holes in the cuticle on the cell surface in the natural drying group were no less than those in the hair dryer at low temperature. And among the several experimental groups, only the hair in the natural drying group showed cell membrane damage. It does not mean that drying your hair naturally after washing is definitely better than using a hair dryer. And it is inconvenient to do anything with wet hair.

So you still have to use the hair dryer, but you have to be careful to control the temperature.
When buying a hair dryer, we need to pay attention to the temperature parameters and try to choose one with high and low temperature settings. Of course, there is no need for too many settings, 2 to 3 settings are enough. Usually, use the low temperature setting to dry your hair, and if you are in a hurry, you can occasionally use the high temperature setting to dry your hair quickly.

Wind speed

Since high temperatures can damage the hair cuticle, it is not practical to quickly dry your hair by increasing the temperature. Therefore, the most important parameter in a hair dryer is the wind speed.

Many businesses will advertise that their hair dryers have high power, so they can dry hair quickly. It should be noted here that the power of a hair dryer is not equivalent to the wind speed. Some hair dryers may only have high power in the heating part. Therefore, compared with the power of a hair dryer, the wind speed of the hair dryer should be paid more attention to.

The wind speed of the hair dryer is an important reference. The picture is taken from the Internet.

Some businesses will not directly announce the wind speed of the hair dryer, but only the motor speed. The speed is indeed related to the wind speed. If there is no wind speed parameter when choosing, the speed can also be used as a reference. In addition, some hair dryers will mark their air volume. If there is this air volume, you can also refer to it.

The speed data can also be used as a reference. The picture is taken from the Internet.

The page with both rotation speed and wind speed marked, the picture is taken from the Internet

Do more expensive hair dryers have faster wind speeds?

It is not absolute. For the convenience of understanding and comparison, the table below shows the price, wind speed, rotation speed and power data of some hair dryers at different prices.

The table data is collected from the Internet

It can be seen that some high-priced hair dryers do have very fast wind speeds, but they are also very expensive. Although the cost-effectiveness may not be the highest, it does improve performance.

However, there are also some hair dryers that are very expensive, but the wind speed is not much higher than that of hair dryers that cost less than 100 yuan, or may even be lower. You should think twice before buying such hair dryers.

noise

According to the World Health Organization, the recommended safe listening time for using a hair dryer is about 20 minutes per week. This safe listening time is based on the volume of the hair dryer at 100 decibels. But if the volume of the hair dryer is lower, the hearing damage caused will also be lower.

WHO's noise volume and safe listening time, Image source: Reference 3

According to WHO data, when the noise volume is 80 decibels, the safe listening time per week reaches 40 hours, which is equivalent to blowing hair for more than 5 hours a day. We can assume that within 80 decibels, the hearing damage caused by hair dryer noise to the ears can be ignored.

Of course, if you don’t like loud noises, you can buy a quieter hair dryer. The only thing to note is that the more expensive the hair dryer, the quieter it is. Merchants usually mark the volume of the hair dryer, so pay attention to it when purchasing.

Negative ions

Today’s hair dryers, ranging from several thousand yuan to just a few dozen yuan, all claim to have negative ion functions that can protect and even repair hair.

At present, there is much controversy about the impact of negative ions on human health. Some studies have indeed shown that negative ions are beneficial to the human body, but some studies have shown that the health of experimental animals exposed to negative ions has not changed. Some literature also believes that negative ions can make the air fresher because they can charge suspended particles in the air, allowing them to adsorb faster and reduce the concentration of suspended particles.

The picture is taken from the Internet

However, these studies did not directly conclude that negative ions can "repair hair". One possible effect of negative ions on hair is that after combing your hair with a plastic comb, the hair may carry a positive charge due to the electrostatic effect, and negative ions can neutralize these positive charges, making the hair less likely to "frizz".

Therefore, if a hair dryer focuses on promoting its negative ion function, but parameters such as wind speed are not particularly good, you need to purchase it with discretion.

In addition, some negative ion generators will produce ozone at the same time as they produce negative ions. If you smell a strong smell of ozone when using a hair dryer, it is not recommended to continue using its negative ion function.

Summarize

To sum up, the most important parameter of a hair dryer is the wind speed. Under the same temperature, the higher the wind speed, the faster the hair will dry. If the merchant does not publish the wind speed, you can also refer to the motor speed data. In addition, when using a hair dryer, it is best to use high wind + low temperature to prevent high temperature from damaging the stratum corneum.

As long as the volume of the hair dryer does not exceed 80 decibels, there is no need to worry about it causing hearing damage. There is currently no research to prove that negative ions can repair hair. It is more effective in reducing static electricity.

References

[1] Patent: US994259A

[2] Lee, Y., Kim, YD, Hyun, HJ, Pi, LQ, Jin, X., & Lee, WS (2011). Hair shaft damage from heat and drying time of hair dryer. Annals of dermatology, 23(4), 455–462. https://doi.org/10.5021/ad.2011.23.4.455

[3]https://www.who.int/zh/news-room/questions-and-answers/item/deafness-and-hearing-loss-safe-listening

[4] Jiang, SY, Ma, A., & Ramachandran, S. (2018). Negative Air Ions and Their Effects on Human Health and Air Quality Improvement. International journal of molecular sciences, 19(10), 2966. https://doi.org/10.3390/ijms19102966

Planning and production

Author: Xiaowei Popular Science Creator

Review丨Ji YangResearcher at the Institute of Semiconductors, Chinese Academy of Sciences

Planning丨Fu Sijia

Editor: Fu Sijia

Proofread by Xu Lailinlin