By Jc of The Natural Haven Bloom

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.

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.

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.

Ladies, do you use castor oil? Has it help improved thickness?

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80 Comments on "Does Castor Oil Increase Hair Thickness and Rejuvenate Edges?"

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She didn’t really answer the question whether it rejuvenates edges. Thickness is one thing, but if you have some traction alopecia and you want to recover your normal thickness back – would castor oil help?

I think she did address it she said this: “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.” I think she is saying that people are equating the benefits of castor oil with castor oil and massage in the case of regrowth. If you are using both castor oil and massage it is… Read more »

I am a black castor oil advocate. I primarly use it on the ends of my hair and to seal in moisture; it works wonders against single strand knots. Not sure about it making my hair thick because my hair is already thick. But I love that castor oil goes a long way, you don’t have to use a lot.

Rachel Natalie

Yes, I love castor oil for sealing. It agrees with my hair and ends.


Castor oil is the best for sealing my edges and ends.




I can understand where castor oil would cause a buildup of particles that would mimic thickness of the hair. I would not use it because of that. I like to use light and non greasy hair products for my hair, especially in the summer and also use a purifying shampoo and conditioner. Thank you for this information 🙂


This is interesting, I was wondering about Caster oil, had it on my list of things to try. My sweetie left some Jamacian Blask Caster oil at my house on accident and he lives out of town so…. I’m gonna start using it in the oil combo I use to massage my scalp with and see if I notice any difference in my growth/thickness.




Interesting i guess Castor oildoes something even if scince doesn’t want toresearch it or validate it. Science is what it is knwledged but when it comes to hair journeys i’m afraid it’s about an idnciduals experience.

I love castor oil it is brilliant added to a deep condtioner and a great source of moisture.


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Love this picture!!!You’re one pretty lady.It is encouraging to see such good hair growth and it is nice that castor oil has worked so well for you!


I have been using Castor oil for the past year (pic right afterBC on 9/10 and now) and I most definetly believe that its had an effect on my hair growth and thickness.. I Love It!



My experiences with castor oil have been very rewarding. My hair has been softer and thicker to the touch <3

Tiffany Madonia

Well, I’ve used Jamaican Black Castor oil on my edges…there were two particular spots where my hair was not growing at all anymore for like 3 years, due to braids that were too tight. I used the JBCO and my hair started back growing….I stopped using it and the hair growth stopped (the hair that had grown did not fall out though).


Hi well for me personally I have suffered with a hairline problem after repetitive times placing my hair in a tight bun or pont tail. A year ago I started to massage the area and a year later i have seen a vast improvement.