I do regularly contribute science articles to BGLH and I am cross posting this one because the question comes up time and time again.
So let us take a straw poll. How many of you have heard that castor oil can help improve the thickness of natural hair? I have seen this said many times, and since hair thickness is dictated by genetics, I have always wondered if there was any truth to the statement. I finally decided to research it from a scientific perspective.
First question - what is in castor oil?
Like many natural oils (coconut oil, shea butter, olive oil etc), castor oil is composed of several fatty acids. In reality, these acids are bound and therefore do not really behave like acids at all (note that you cannot pH an oil as it does not dissolve in water). The dominant fatty acid in castor oil is ricinoleic acid.
Can ricinoleic acid or any other of the fatty acids in castor oil increase hair thickness?
There are no scientific studies to prove that castor oil can increase hair thickness. Interestingly, in the field of male pattern baldness where hair thickness improvement is a major requirement, castor oil does not even feature as a research ingredient. Many of the other fatty acids in castor oil are similar to those found in coconut or olive oil and these are not associated with increasing hair thickness either.
What about the pictures where naturals show an improvement in hairline/bald patches by rubbing castor oil?
In my opinion this is not evidence because massaging in itself even with plain water can stimulate regrowth of hair (i.e where hair has fallen out or been pulled out, massage can help a new strand to grow back). I would add though that the study that showed this was done in rats and not humans.
Additionally, I have not seen anyone measure the actual diameter of hair to show that castor oil use has thickened their hair. Some people refer to thickness as the overall density of hair and in my view again this is not proven by the pictures as often they are just referring to normal regrowth.
Could something else be at work?
My theory in discussion with my chief chemist (i.e the husband) is that castor oil perhaps can stick to hair more firmly than most oils and therefore create an illusion of thickness. Anyone who has used it will note how thick and viscous it is. It is almost like a soft glue and tends to stay put and not move when applied. It does not transfer easily either, which means that it can attract small particles of dust and lint which may also add to the illusion of thickness.
Do you really need to change your hair thickness?
In my view, I think that life and biology is about diversity. Not everyone can have thick hair strands, not everyone can have high density hair but everyone can have great hair regardless of how thick the strand or how dense the hair .
Do you think that castor oil can thicken hair? What is your experience with it?