There is no scientific evidence that castor oil promotes hair growth, according to Healthline. Hair growth results from stimulation of the hair follicle beneath the skin's surface as it pushes the connecting hair shaft upward above the skin, explains WebMD.
Castor oil, which derives from the seeds of the castor bean plant, or Ricinus communis, possesses antiviral properties, notes Healthline. This makes the topical application of castor oil a popular treatment for abnormal skin conditions, including claims that it can help combat skin cancer. However, the American Cancer Society states that there is no clinical support for this. The use of castor oil as a laxative is anecdotal.