Oral castor oil is something not thoroughly explored in the hair loss community, despite a significant amount of promising data backing its potential efficacy.
Typically, castor oil is topically applied.
In practical application, its effect on hair loss prevention topically seems to be minimal when it comes to dealing with androgenic alopecia as opposed to a skin condition.
To get adequate absorption through the scalp you would need to mix castor oil with DMSO, or keep it on your scalp almost all day.
And even with this, topical absorption is subpar relative to oral castor oil ingestion.
The component of castor oil that was found to potentially be hair protective is the Ricinoleic acid found within castor oil itself.
In theory, this could help relieve hair follicle hypoxia by antagonizing the tissue constricting effects of Prostaglandin D2 (PGD2) in the scalp [R].
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What is PGD2 and PGE2?
Without going too deep into the topic, PGD2 and PGE2 are physiologically active lipid compounds that are categorized as prostaglandins.
Prostaglandins exhibit diverse hormone-like properties and are found abundantly in human tissues, such as the organs.
At their most basic, PGD2 causes the constriction of tissues in the body, while PGE2 does the complete opposite by inducing tissue relaxation [R].
PGE2 and PGD2 more or less counterregulatory hormones of one another.
PGE2 Protection Against Radiation-induced Hair Loss
PGE2 was found to prevent radiation induced hair loss in a rodent model [R].
Although it has not been tested on humans, the data suggests that a favorable ratio of PGE2 to PGD2 has significant hair protective benefits.
In cancer patients that would otherwise lose their hair, PGE2 has the potential to protect them from radiation-induced hair loss.
In theory, castor oil could potentially facilitate the same hair protective benefits.
PGE2 And Castor Oil To Induce Labor
PGE2 is commonly used to induce labor [R].
The mechanism by which it facilitates this is by relaxing smooth muscles, softening the cervix and causing uterine contractions.
Studies have noted that PGE2 is hair protective, and PGD2 inhibits hair growth [R].
Notably, castor oil is also used to induce labor [R].
The ingestion of the Ricinoleic acid in castor oil induces formation of Prostaglandin E2 (PGE2) and acts as a potent agonist of EP3 and EP4 receptors, consequently facilitating the same labor induction effects of pure PGE2.
Another interesting thing to note is that, this belief is more than just conceptual.
It’s actually being deployed as a medical practice.
For example, if a woman desired to give birth on a specific date, they may be prescribed PGE2 in conjunction with a large dose of castor oil.
As for the dosage, women are given upwards of 4 tablespoons (60 mL) of castor oil for labor induction.
Castor Oil As A Laxative
Castor oil is most commonly used as a laxative.
It is a treatment for constipation, and works the same way it induces labor.
Smooth muscle relaxation helps alleviate constipation and encourage a bowel movement.
As a laxative, doses above 5 mL are commonly used, although many will assert that anything above a 2 mL daily dose will cause the same laxative effects.
Castor Oil and Hair Loss
So how castor oil is used against hair loss?
Understanding that the mechanism by which PGE2 works starts to shed some light on how the cascade of events leading to hair follicle miniaturization occurs.
PGE2 relaxes tissues in the body, hence why it works to induce labor and as a laxative, and also why it is also potentially hair protective.
It relaxes the tissue that would otherwise be constricting hair follicles and potentially causing follicular hypoxia.
For inducing labor, doses upwards of 60 mL of castor oil are used.
As a laxative, doses upwards of 5-15 mL of castor oil are used.
In a hair loss prevention context, doses of 0.5-2 mL of castor oil per day have proved to be sufficient, and it is theorized that 2 mL is where diminishing returns sets in.
The tolerability of castor oil consumption on a daily basis more or less boils down to digestion and gut health.
Right off the bat, one major complaint that some report with oral castor oil consumption to treat hair loss is that it causes an upset stomach.
I know guys who can handle upwards of 5 mL per day with no issues, and I know guys who can't even consume 0.5 mL per day without massive digestive stress.
This is a relatively obscure potential treatment, so proceed with caution.
There are not many studies we can refer to to assess its safety and tolerability when it comes to long-term usage, as this is ultimately what we would be interested in in a hair loss prevention capacity.
Data outlining its tolerability as a laxative shed light on its safety in the short term, but for daily use at micro-doses for years on end, that remains to be seen.
According to the Food and Agricultural Organization and World Health Organization, up to 0.7 mg/kg of castor oil orally per day is safe for men [R].
Oral castor oil is also generally recognized as safe and effective for use as a stimulant laxative by the FDA [R].
Mega Dosage of Castor Oil and Its Effect on Hair Growth
One of my close friends started taking 5 mL per day for beard growth.
While he's not particularly concerned with hair loss prevention, the results he reports are still useful to reference as the mechanism by which beard hair growth is facilitated is not different than on the scalp, it just doesn't have a cascade of hypoxia triggering factors causing miniaturization like on the scalp via androgens.
This friend of mine, who was the subject of his own experiment, noticed a positive result in just a couple weeks.
The sides of his beard had become significantly less patchy, his beard had become thicker in general, he had grown hairs in areas which did not have any hair growth before, and his beard is now darker as well.
It should be noted that I don't recommend using this high of a dose, but it is insightful to reference his results at 5 mL nonetheless.
Minoxidil And Oral Castor Oil As Growth Agonists
Minoxidil is commonly used to increase beard hair growth.
If something works to increase beard hair growth, you can logically conclude it would likely have a similar effect on the scalp as a growth agonist.
This isn't common with topical Minoxidil as it more or less stays localized to its area of application and only is partially systemically absorbed, but with oral Minoxidil (Loniten) hair growth everywhere is reported in almost all users.
Oral castor oil seems to facilitate this systemic increase in hair growth, but without the negative cardiovascular effects that Minoxidil is associated with.
The reason why is that both of these compounds increase circulation to the scalp, thereby alleviating the follicular miniaturization occurring in the tissue.
Ultimately, these are both just bandaids for the root of the issue (endogenous androgens), but at the end of the day, the more tissue relaxation and circulation you can promote the better for antagonizing the constricting effects triggered by androgenic hormones in the body.
The mechanism by which they accomplish this likely differ, as Minoxidil mainly works by opening up the potassium channels in the body, while oral castor oil works by inducing the formation of PGE2 and acting on the some of the same receptors as PGE2.
However, Minoxidil's mechanism of action isn't fully understood either, and a lot of the data actually suggests that it doesn't just work by opening up the potassium channels more, but it also may have an anti-androgen like effect, and it may even be a PGE2 agonist in itself too [R, R].
Known Factors of Hair Loss
While nobody definitively knows what the full cascade of events is in the body that lead to follicular miniaturization, it seems that androgens are a catalyst for scalp tissue changes that ultimately lead to poor circulation and cumulative hypoxia.
Ultimately, poor circulation and the presence of androgens go hand in hand, and interventions that increase scalp tissue circulation all seem to have positive effects on hair growth.
Hence, the most effective treatments for staving off further miniaturization would include compounds that antagonize the effects of androgens either at the androgen receptor itself, or systemically.
My View On Oral Castor Oil For Hair Loss Prevention
Some reputable sites seem to deem that castor oil is safe to consume long-term [R].
However, I am still wary of any potential long-term ramifications it could have on gut health in particular, and will proceed with caution.
Its potential efficacy is promising, as it evidently has a profound antagonizing effect against the tissue-constricting effects of PGD2, and is seen in the medical community as one of the go to agents to facilitate this.
Anecdotally, it seems to be one of the most promising growth agonists in a hair loss prevention context with a fairly low risk profile.
I will be experimenting with 1 mL per day myself, and will make a judgment after I've given it a fair chance as to whether or not I think it holds its own to justify its use in a hair loss prevention capacity for most men.
Is PGE2 More Effective Than Castor Oil?
We already know that the way castor oil facilitates its potential benefits in a hair loss prevention context is via the formation of PGE2 and activation of some of the same receptors as PGE2.
So if that is the case, then why don't we just apply PGE2 to our heads and be done with it?
Well, in practical application, while it seems to have some positive effect, it isn't enough to stave off androgenic alopecia.
However, it certainly doesn't hurt, and many individuals I know have noted that oral castor oil gave them better results than topical application of pure PGE2.
The problem with straight PGE2 is that PGE2 dosages are extremely small and measured in micrograms, making it very difficult to make an accurately dosed solution that doesn't overload your scalp with excessive PGE2, and the potential ramifications of that are unknown.
PGE2 is also cost prohibitive, whereas castor oil is dirt cheap, seems to facilitate much of the same effects at a fraction of the price, and there is a lot of data supporting the safety of the consumption of castor oil at dosages far exceeding what someone would consume in a hair loss prevention context.
Consuming a small dose of ricinoleic acid as a precursor to PGE2 also gives your body a chance to regulate how much PGE2 is formed, whereas with straight PGE2 application you are forcing your body to deal with a giant hit of PGE2.
The potential contraindications of PGE2 use are worrying as well, as it is directly tied to the promotion of cancerous tumour growth [R].
Where To Buy Food Grade Castor Oil
You want to buy 100% castor oil, not Jamaican black castor oil.
It's clear and a pale yellow color.
Food/Pharma grade (USP or BP) is ideal as it ensures a high enough standardization of Ricinoleic acid.
Ricinoleic acid is the component of castor oil that boosts PGE2 and we care about.
NOW Solutions Castor Oil is third party tested and meets our criteria for a high quality Castor Oil, and is also what I use personally.