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