I've been using castor oil on my scalp & hair for the past 2 years. I didn't realize it was called castor oil until recently. I'm originally from Haiti, but came to the U.S. very very young, growing up my mother would often massage us with what I came to know as "Palma Christi". It wasn't purchased in a store though and it seemed to be an endless supply (a little went a long way). She would heat up a bit of the palma christi (and a pinch of salt) in her palm by rubbing them together and massage deeply into what ever area was hurt or sprained and sure enough by the next day it didn't hurt. Note: This is in no way intended as medical advice. Research has found traces of toxins so please decide for yourself. Two years ago while doing research re fibroids I kept seeing something called "Palm of Christ" and I realized that was what my mom used (and continues to use). It was used as a heated oil treatment on the abdomen. After I got it I also started using it on my feet after I came out of the shower (it's kind of tricky) about a month in my feet were soooooooo soft.....I thought to myself hmmmmmm? So on my head it went. Whenever I air dry which up until 2 months ago was always, I would put a thin (and I do mean thin a little goes a long way) layer in my palm, rub my palms together making sure I got it on my fingers as well. Then I would massage my scalp with my fingertips. Afterwards I would run my palms and fingers lightly through my hair and finish off with gathering my ends together...running my fingers around them. I would do this daily mind you but only because I wet my hair daily when I showered in the a.m.
As I said it wasn't until 2 years ago I even heard the words castor oil and upon further research realized that castor oil and "palma christi" a.k.a. "palm of christ" were all the same thing. It has medicinal/healing qualities (hence the name "palm of christ"). I purchased the "Heritage" brand. So castor oil is pretty incredible IMO. I totally dig it's softening/healing effects. I even recommended it to a friend whose husband had feet as rough as brillo pads (according to her) and they are smooth as anything now. He used it for 2-3 months though.
I'm not using it now because I purchased a gi-normous bottle of it and it's back home in GA, right now I'm away for studies and I didn't want to risk a travel size bottle of it opening up in my suitcase crammed with a culmination of 2 years worth of homework material. So I'm blow drying and I haven't tried it in conjunction with the blow drying.
I know that people have been given castor oil when they were young as an oral medication. I never used it orally so I can't say anything on that.
I hope that helped,
CG
Below are some links:
http://naturalmedicine.suite101.com/article.cfm/castor_oil
http://www.annieappleseedproject.org/castoroiluses.html
http://www.bhavinexport.com/castor.html