You may have read online that castor oil can be used to re-grow thinning hair, patchy eyebrows, or sparse eyelashes. But is there any science behind this popular internet claim?
To find out, I started with a search of the National Library of Medicine (Pubmed)–a database of all published studies on substances synthetic and natural alike. Castor oil has been used for many years to help ease osteoarthritis, and there is a limited body of evidence confirming this practice. However, searching for any articles regarding its ability to re-grow hair came up empty.
After searching many variations of “castor oil” and “hair,” through Pubmed and continuing to find no results, I took to the general internet and found this article. It says the science behind castor oil's ability to re-grow hair is such:
Accounting for more than 90% of castor oil’s constitution, ricinoleic acid is the single largest component, is mono-unsaturated and features 18 carbons. What renders it different is that its 12th carbon comprises of a hydroxyl functional group. It is courtesy of this structure of ricinoleic acid that castor oil derives its polar nature and hence is chemically more nourishing for the scalp.
Hair growth is spurred by a lipid compound named Prostaglandin (PGE2) and it could be best described as a catalyst. While its presence in high concentration promotes growth of hair, its depletion causes hair loss and eventually leads to baldness. Castor oil’s principle component – ricinoleic acid – has been scientifically proven to stimulate the production of Prostaglandin (PGE2) when applied to the scalp. Enhanced production of this lipid, particularly in bald spots, enriches hair follicles and encourages regeneration of hair.
It sounds legitimate–there are chemical names and diagrams, and even sources cited. But the science behind the claims have been misinterpreted in more ways than one.
Yes, the fatty acids in castor oil are primarily ricinoleic acid. However, oils don't just contain free fatty acids. In castor oil, the fatty acids are arranged in to molecules called triglycerides: three fatty acids held together by a glycerol group. (Aka glycerin.) So, while castor oil can easily be broken down to extract ricinoleic acid, castor oil in its raw state doesn't contain free ricinoleic acid. Putting castor oil on your skin and hoping it will affect your prostaglandins is like putting a bottle of Aspirin on your head and hoping it will get rid of your headache. Essentially, the ricinoleic acid is still in its “wrapper” in castor oil.
I did find one study that shows how ricinoleic acid can affect prostaglandins, however, it was when taken internally. The digestive system is able to break down the castor oil and turn it in to free ricinoleic acid, which can interact with prostaglandin receptors and create a laxative effect and potentially be used to induce labor. Prostaglandins do have some kind of mechanism in the hair follicle, however, their function continues to be unclear. And the effects of putting ricinoleic acid on hair is also unclear.
Castor oil is a safe ingredients to use, and I am sure that there are reports that it appears to have helped re-grow hair for some people. However, there is no science to back these claims.
What about you? Have you tried castor oil to spur hair growth? What were your results?
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