Castor oil is used in massage therapy to relax tense muscles and reduce inflammation prior to, in addition to, or after, a massage treatment. Let's investigate...
ABOUT CASTOR OIL
Castor oil is created by pressing seeds of the plant Ricinus communis. The name "castor oil" has a crazy complex and speculative-laden history, which likely derives from its use as a replacement for castoreum.
Castoreum is a perfume base made from the dried perineal glands of the beaver. Castor means beaver in Latin. In fact, a synthetic version of castoreum is still being used in many of today's perfumes. Hrm, the more you know, right?
Castor oil and its derivatives are also used for a variety of other things: paints, lubricants, brake fluids, waxes, and nylon just to name a few. Its versatility is amazing.
A study published in 2006 showed castor oil polymer, "assisted cicatrisation process, was biocompatible without inflammation, and it can be used in joints as an alternative for bony filling".
Traditionally, it's been used as a strong laxative when ingested orally and has since been deemed by the FDA as "generally recognized as safe and effective" for over-the-counter use as such. This is because when castor oil is ingested, ricinoleic acid (which we'll talk about later) latches onto EP3 molecules in smooth muscle cells on the walls of the small intestine. This leads to contractions, which provides reason for castor oil’s effectiveness as a laxative.
It's also been used traditionally to facilitate labor; however, a 2014 review stated very few scientific data support such an indication.
In terms of massage therapy, we need to look at its topical functionality. What makes castor oil packs tricky to investigate is that it's not always used by itself. It's commonly used as a "castor oil pack" which consist of applying layers of castor-oil-soaked fabric directly on the skin with a heat source (electric heating pad, hot pack, etc) added on top.
Heat by itself causes changes within the body, and it's a tool for pain relief all its own. So for the purpose of this article, we'll focus just on the oil, and what's in it.
CASTOR OIL ACTIVE INGREDIENTS
About 85-95% of castor oil is ricinoleic acid. For those familiar with the show Breaking Bad, or know of writer Georgi Markov's assassination that involved an umbrella, the ricin within ricinoleic acid should sound familiar.
The castor seed does in fact contain the toxic protein ricin, which when injected or ingested is a fairly nasty way to die. However, the heat involved during the oil extraction process causes the protein to become inactive. Good thing.
A study published in 2000 on ricinoleic acid states, "Observational studies indicate that topical application of ricinoleic acid (RA), the main component of castor oil, exerts remarkable analgesic and anti-inflammatory effects. Pharmacological characterization has shown similarities between the effects of RA and those of capsaicin, suggesting a potential interaction of this drug on sensory neuropeptide-mediated neurogenic inflammation."
Some muscle relief products off the shelf include capsaicin to alleviate mild to moderate aches and pains. So any potential similarities between capsaicin and ricinoleic acid is certainly interesting.
However, what seems unclear in the research to date, is how effectively the body absorbs castor oil through the skin. A study published in 2000 that compared oral and topical administration of the oil via urine analysis concluded, "Castor oil is either not well absorbed through the skin or is metabolized in a way that did not have the effect of significantly increasing the excretion of the specific metabolic byproducts associated with the ingestion of castor oil."
Approximately 2-6% of castor oil is oleate acid, which is a common fatty acid derived from animal or plant fats. The term "oleic" means related to, or derived from, oil or olive.
A team of researchers based at McMaster University have discovered that oleic acid's smell may indicate danger or a "death signal" to living insects. The smell causes them to avoid their kin that are diseased, dead, or had unfortunate run-in with predators. The team found that a "drop of oleic acid on a perfectly healthy ant resulted in her being carried kicking and screaming to the [colony's] cemetery. Ants can't scream, but you get the picture."
Despite that fascinating aside, there does not seem to be evidence that suggests oleate acid has medicinal topical application for those of us with endoskeletons.
Approximately 1-5% of castor oil is linoleic acid, is a polyunsaturated omega-6 fatty acid. The term "linoleic" comes from the Greek word linon (flax). This oil is also linked to the insect "death signal" discussed above.
Linoleic acid has become an increasingly found ingredient in the beauty products due to properties beneficial to the skin. A 1998 double-blind placebo-controlled randomized cross-over study pointed to acne reduction when applied on topically and a double-blind, randomized clinical trial published in 2002 concluded, "topical application of linoleic acid is considered to be effective in the treatment of melasma patients." Melasma is irregular darkening of the skin, most common in pregnant women.
CASTOR OIL SUMMARY
I found an a limited body of research that may suggest the use of castor oil for pain relief and inflammation. Given the very low risk and very limited side effects, it would seem worth a try for individuals seeking a complementary and/or natural remedy for pain relief.
But the jury is still very much out. The big trip up is: can castor oil be absorbed through the skin? If not, as the most predominate study suggested, its possible analgesic and anti-inflammatory effects are moot.