There is slight scientific evidence that Castor Oil (CO) stimulates hair growth. I only found some theoretical evidence, which I will share below.
Let me try to explain how CO promotes hair growth, as it is asked numerous times and many times not explained. It's a good way to understand the process myself and give some info back.
For the CO I will give you guys some scientific references, so you can verify my statements and read on about the usefulness.
Basis knowledge on Androgenetic Alopecia:
Your androgens increase Prostaglandin D2 synthase (PTGDS), which inhibits hair growth by Prostaglandin D2 (PGD2) in your scalp. Secondly, depletion of Prostaglandin E2 (PGE2) inhibits hair growth, and it's presence promotes hair growth.
Why Castor Oil may promote hair growth?
- CO consists of about 84% of Ricinoleic Acid (RA)[1]. RA is able to inhibit PTGDS, by binding to PTGDS (residues Tyr152, Met99, Trp104, Ala105, Met 11 and Arg14), and in turn inhibits the amount of PGD2 in your scalp [2].
- Secondly, RA stimulates the production of PGE2, it binds to two of the four receptors of PGE2, namely EP3 and EP4[3]. Topical pure PGE2 binds to all 4 receptors. Pure is hard to get and very expensive for most people.
- Thirdly, it could be that RA's anti-inflamatory, -bacterial, -viral and -fungal properties have a healthy effect on your scalp. I did not searched into this third effect.
(Be aware you need to use more substances to stimulate hair growth, as CO is just one part of so many important processes you either need to inhibit, block or stimulate.)
Vehicle for Castor Oil:
CO's thick and viscous yellow liquid is highly hydrophilic, which makes it
impossible to penetrate the skin [3]. Therefore you need a
penetration enhancer like Ethanol 95% (or higher), Dimethyl Sulfoxide (DMSO) or Dimethyl Isosorbide (DMI). I have only experience with mixing it with DMSO. For the info, my DMI was about 3 times more expensive than my DMSO. I am not sure how much DMI you would need, could be less than DMSO.
At this moment I am using 67% Home Health's CO from iHerb with 33% DMSO (99,99% purity) from Regency Labs on eBay. But of course you can decide to buy other brands. Both looked very pure to me, and both are manufactured in the USA. AS I live in Europe, I had to import these. This CO is unrefined and cold pressed, which has being said to be important for hair growth use.
Vehicle on DMSO:
It takes about 15 minutes to penetrate with this vehicle, without DMSO it just stays on top of my head until I wash it out. I have tried it with 20% DMSO, but that's too little; it stays sticky, and it just partly penetrates my skin. From my experience I would say 40% of DMSO would be even better than 33%.
Be aware that DMSO freezes below 17 °C, and it will sink to the bottom, even after mixing well above 30 °C. So it's important to shake the bottle with mixture before using. Any plastics of the bottle should be made of HDPE, otherwise it will melt the plastic. If you have a glass bottle, the cap of the bottle should be of HDPE!
Although I have HDPE bottles, I was mistakenly using a non-HDPE syringe and non-HDPE pipette, which were melting by the DMSO. The mixture got contaminated, and I had to make a new one.
I am thinking about changing the vehicle because of the large amount of DMSO.
ANY ADVICE IS WELCOME. I have Propylene Glycol, Ethanol 95%, DMI and PolySorbate 80 directly available.
Next to topical CO, I take 1300mL orally by taking two capsules from the NOW brand from iHerb. I also started using Rosemary Oil (RO), which contains Carnosic Acid (CA), and is less sticky than CO, it penetrates more easily and quicker and feels much better than CO on the skin. CA itself does not increase PGE2 production, but many of it's derivates do [4]. I have to read more into this, but I think RO could be second important oil to CO.
I also bought pure L-Menthol crystals and pure Peppermint Oil. Unfortunately I found an article on Pubmed concluding Mentha Piperita Oil inhibits PGE2 production by 40% at already 0,01%/mL!
Okay, I hope this was helpful.
MindfluX
References
1 Wang, M.L., Morris, J.B, Tonnis, B., Pinnow, D., David, J., Raymer, P., Pederson, G.A. (2011). Screening of the Entire USDA Castor Germplasm Collection for Oil Content and Fatty Acid Composition for Optimum Biodiesel Production.
Journal of Agricultural and Food Chemistry, 59, 9250-9256.
http://pubs.acs.org/doi/abs/10.1021/jf202949v
2 Fond, P., Tong, H.H.Y, Ng, K.H, Lao, C.K., Chong, C.I., & Chao, C.M. (2015). In silico prediction of prostaglandin D2 synthase inhibitors from herbal constituents for the treatment of hair loss.
Journal of Ethnopharmacology, 175, 470-480.
http://www.sciencedirect.com/science/article/pii/S0378874115301677
3 Tunaru, S, Althoff, T.F., Nusing, R.M., Diener, M. & Offermans, S. (2012). Castor oil induces laxation and uterus contraction via ricinoleic acid activating prostaglandin EP3 receptors.
Proceedings of the National Academy of Sciences of the United States of America, 109, 9179-9184
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3384204/pdf/pnas.201201627.pdf
4 Theoduloz, C, Pertino, M.W., & Schmeda-Hirschmann, G. (2014). Gastroprotective Meachanisms of Action of Semisynthetic Carnosic Acid Derivatives in Human Cells.
Molecules, 19, 581-594.
http://www.mdpi.com/1420-3049/19/1/581/pdf