Sunday, 25 August 2013

Could air drying actually damage your hair?

While browsing through the forums at LHCF, I found a link to an article that was really curious! Scientists in Korea had reported that drying hair with a hair dryer on a low temperature* was actually less damaging than air drying naturally at room temperature (Ann Dermatol, pp 455–462, 2011).

They have got to be kidding, right? Well not really. They first found that drying hair at high temperature was quite damaging to the cuticle with holes and cracks appearing after 30 days. However, they found low temperature blow drying did not severely damage the cuticle in this way which made it therefore comparable to natural air drying which does not damage the cuticle.

The big difference was that damage to the inner cuticle layer was noted with air drying but not with low or even high temperature blowdrying. Here are some diagrams to refresh your memory on the structure of the cuticle.

Each cuticle is made up of several layers

Each layer is 'glued' together by a mix of lipids (oil like substance) shown in yellow between layer 4 and 5

It is this internal layer of lipid/cuticle cement that appears to be affected by natural air drying and the scientists suggest that it is the prolonged time that it takes for hair to dry that is damaging. In other words, the longer you keep your hair wet, the more likely you are to affect the internal cuticle cement because the additional moisture can cause it to swell and therefore weaken.

So on to the Q&A

1. What type of hair was studied, was it damaged?
Although not specified, it was most likely Caucasian in origin and the study does specify that it was untreated natural hair (therefore never previously coloured)

2. Is this study valid?
I think that there are certain things in the study that many people with natural hair would not do but this does not invalidate the findings. I do have some concerns critically with portions of the work but again, this does not mean the study was wrong.

3. What would people with natural hair not do that was done in the study?
The study involves washing hair daily with an SLS shampoo. There is no conditioner used at all. SLS is one of the most aggressive cleansers out there and most naturals would restrict it to a clarifying option as opposed to daily use. Very few naturals actually shampoo daily and most naturals would almost always use a conditioner.

However, all these arguments do not invalidate the study because the low temperature blow dried hair had the same harsh daily wash and did not show damage to the inner cuticle cement.

4. What concerns do you have with the study?
My only issue with the study is the lack of numbers. They do show pictures of the damage from airdrying but do not say statistically how many of the strands they looked at showed the damage. If the damage was found in 1 out of every 30 strands, this is hugely different from 20 out of every 30 strands. Could that image have been a fluke?

5. So is air drying really more damaging than low temperature blow drying?

I am going to say that I am not 100% confident in that statement for the following reasons

a) I think that using a mild shampoo and following up with a conditioner is essential, this study did not do that. Remember that hair conditioners do help to mitigate the effect of shampooing.

b) I also think that daily shampooing is really not ideal for most natural hair. If you shampoo or even wash your hair every day, you should perhaps think about a low temperature blow dry. However, if you do not, air drying is probably still the better option

c) I do like that the study has highlighted that it may be possible to damage hair by keeping it wet for prolonged times. I do actually think that this is very likely and it is why I do not support conditioning hair for prolonged times or even giving hair 2-3 days to dry post wash. I am just not entirely convinced by the single image that air drying is worse than low temperature blow drying.

Extra reading - Ceramides and their role in patching up the cuticle cement

*Low Temperature Blowdrying - 47°C/117 F, held at a distance of 15cm/6 inches away from the hair


  1. The Beauty Brains "reviewed" this paper not long ago and their conclusion was although low-heat blow-drying is "better", theoretically, for the CMC; it caused more surface damage. If I understood you're saying that the study came to the conclusion that low-heat blow-drying does not cause that surface damage, being comparable in that with air-drying? Like, if we follow the study, low-heat blow-drying would be the best option because it generates no significant damage for example to the surface of the hair an prevents or lessens damage to the CMC?


    1. I am going to edit the article, the study came to the conclusion that there is some minor surface damage with low temperature blow drying which is why it is not regarded as not serious.

  2. Hi JC,

    Very interesting!! I believe that air drying is less damaging to the hair myself. JC, you mentioned that leaving conditioner on the hair for long periods of time damages the hair. Why is that true? I used to do the bagging method which entailed applying water and a moisturizer to the ends of my hair and covering them with a ziplock back. This method overmoisturized my ends and made them weaker. Maybe this can apply to leaving conditioner on for extended periods of time. JC, what are your thought on this matter?


    1. I did an article about overconditioning here -

  3. Hey JC, great post!!!
    Can you do a post on direct heat verses indirect heat? Ie: hand-held blow dryer vs. a roller set under a hooded dryer. There is a perception that roller setting is less harmful than blow drying. I am wondering if this is really true and whether you can still cause damage if the hooded dryer is above a certain temp. I am curious to know whether low-temp blow drying is safer than high-temp hooded drying.

  4. Very interesting stuff; I always suspected this might be true as when I used to blow dry on a low heat my hair actually felt smoother and 'recovered' more quickly from washing (weekly/fortnightly). However, once I started air drying religiously, my hair always seemed to feel rougher surface-wise, as though the cuticle on each strand wasn't lying as flat. Despite this I've still been air drying...and smoothing(!) ....Help!


  5. Hey JC,
    I have read this article and while I had some questions, as someone with a background in science what I took from this article was not in a literal sense but a logical sense. Even if no one uses SLS poo, I am under the impression that the effect is keeping the hair wet for a prolonged period, regardless of its state, will cause a degradation of the cmc layer. You are right that the numbers are not great, but the interest in the study is there to speculate if it could be a problem.


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