Castor oil can help regrowing hair.
There is absolutely no scientific evidence to support the claim that castor oil can help regrowing hair.
There are over 17 million results online for the search term ‘castor oil and hair’. These claims date back to the very beginning of the internet. According to numerous popular blogs, hair can grow at 3 to 5 times the normal rate with the regular topical use of castor oil. The castor oil may be blended with another less viscous oil for ease of application and massaged into the scalp and hair twice weekly. There are numerous commercially available brands of ‘castor oil for hair growth’.
Closer examination of the 17 million online results for the search term ‘castor oil and hair’ shows that not a single one of these results comes from the medical or scientific literature. Specifically, there is no clinical trial, observational study, case report, animal study or even laboratory data on the relationship between castor oil and hair in the medical or scientific literature.
Expansion of the search criteria in the scientific literature from ‘castor oil and hair’ to Ricinus communis (which is the official name for castor oil) and alopecia (which is being the medical term for hair loss) did yield a single positive result. The study in question had nothing to do with hair growth. It appears that Ricinus Communis Agglutinin I (RCA1) is the scientific name for a technique that histopathologists use when examining biological specimens such as the hearts of zebrafish (1).
In summary, there is nothing in the scientific or medical literature to support claims that castor oil helps regrowing hair. Claims that castor oil can help with regrowing hair are simply false, misleading and illegal.