I know, I know: We're constantly bombarded with reports of miracle hair growth oils and shampoos and conditioners that promise to reinvigorate our scalps, wipe out build-up, and generally change our hair forever. But before you write off castor oil as yet another beauty fad, consider that this ingredient has a centuries-long history that dates all the way back to ancient Egypt. Plus, castor oil is backed by dermatologists and hair experts as an effective way of quenching dry strands and potentially stimulating healthy hair growth. Curious? We were, too. So we tapped the experts to get more intel about using castor oil in your hair.
The Benefits of Castor Oil
"Castor oil can help to condition hair strands and increase shine and hydration," explains Dr. Rebecca Marcus, a board-certified dermatologist and founder of MaeiMD.
Atlanta-based dermatologist Tiffany L. Clay, M.D. explains that if you looked at the molecular structure of castor oil, you'd see that it's a glycerol with a long-chain fatty acid. So what does this mean? Simply put, fatty acids are excellent at nourishing hair follicles. The outer layer of the hair shaft is covered in tessellating, scale-like structures called cuticles, and when the hair is damaged, those become flayed and flared, resulting in frizz and dullness. Castor oil, however, "can seal and allow the cuticle to lie flatter," according to Clay, resulting in better shine and decreased frizz.
Castor Oil for Hair Growth
"While there are currently no conclusive clinical studies proving that [castor oil] causes hair to grow faster, we do know that castor oil stimulates prostaglandin E2, which causes vascular dilation and increased circulation, which could help to stimulate follicles," says Dr. Marcus. "Another prostaglandin, PGD2 has been shown to be increased in those with hair loss, and castor oil is known to inhibit PGD2. While we are still unsure whether or not these actions cause hair to grow faster, at the very least it may help prevent breakage, contributing to overall length of the hair."
NYC-based dermatologist and hair loss specialist Dhaval G. Bhanusali, M.D. agrees. "There is some proposed benefit of castor oil with improving penetration of topicals and even hair growth," he says. "That being said, I don't think the scientific evidence is there to make any sizable claims, particularly for stimulating new hairs." If you're suffering from hair thinning or hair loss, Dr. Bhanusali says, "I can't stress enough how important it is to go see a board-certified dermatologist. We now have so many new options and it's much easier to create a comprehensive plan for early hair loss than later in the game."
In short, much like a hair growth shampoo, while castor oil alone won't cure hair loss or thinning, it can support hair health, plus make your scalp a better environment for hair growth and retention in the long-term.
How To Apply Castor Oil
For use as a leave-in treatment, Dr. Clay recommends warming a small amount of castor oil between your palms and smoothing it along the ends of your hair on a weekly basis. Meanwhile, for use as a deep conditioner, Dr. Marcus says, "Before washing your hair, I recommend applying it to dry scalp and hair, covering with a shower cap, leaving in for 20 minutes, and then shampooing and conditioning as normal."
However, as with any hair oil, it's important to start small and be aware of how your hair type responds to oil products. "For those with coarse, curly or dry hair, they may wish to apply castor oil to the ends of hair and leave in, as it’s a fairly light oil," says Dr. Marcus. "For those with fine or thin hair, though, they’ll probably prefer to use it as a pre-wash treatment as above, washing out so as to avoid weighing hair down and a greasy appearance."
And if you're not comfortable using pure castor oil for fear of overdoing it, there are a number of less intense options, including shampoos, conditioners, hair masks, and serums.