For years, the beauty industry has collectively touted the benefits of drenching our strands in basically every kind of oil you can think of. Coconut, olive, black seed (Kim Kardashian West's personal favorite), jojoba, and even more delicate essential oil offerings like rosemary, lavender, and cedarwood have all been praised. But there's another oil that's been raising an eyebrow for being a life-changing hair growth oil: castor oil.
Many people (Byrdie editors included) have experienced impressive results after applying castor oil to their brows with the goal of increasing hair growth. Naturally, this bodes the question: Shouldn't the age-old remedy work the same type of magic on the tops of our heads?
Here at Byrdie, it's our job to take hair health and our never-ending quest for luminous, shiny strands seriously. So we wanted to dig a little deeper into this hair growth oil and all its glossy potential. To help us out, we turned to experts for some answers to the question: is castor oil truly effective for hair growth?
Meet the Expert
- Rachel Nazarian, MD, is a board-certified dermatologist at Schweiger Dermatology Group in NYC. She is experienced in a range of dermatologic practices including cosmetic treatments, skin cancer, general dermatology, and dermatologic surgery.
- Philip B. is a Los Angeles-based hair and scalp expert, as well as the founder of Philip B. Haircare.
- Ginger King is a cosmetic chemist, owner of product development firm Grace Kingdom Beauty, and founder of lip care brand Fan Love Beauty.
Keep reading to learn more about castor oil's benefits for hair.
What is Castor Oil?
Castor oil is a nutrient-dense oil extracted from castor beans. It has many medicinal, household, and pharmaceutical uses, and is also widely used in skincare and cosmetics for its potential healing properties.
- Type of Ingredient: Hydrator, strengthener.
- Main benefits: Nourishes the scalp and protects strands.
- Who should use it: Those who are not pregnant (anecdotal evidence suggests that castor oil can induce pregnancy) and those looking for a treatment to nourish dry strands.
- How often can you use it: Use once per week for 20-30 minutes as a treatment. It is an oil, so a little goes a long way.
- Works well with: Carrier oils such as coconut (or other ingredients that impart moisture to hair).
- Don't use with: There are no known ingredients that negatively interfere with castor oil.
Benefits of Castor Oil for Hair
Castor oil has been claimed to have a slew of benefits including strengthening strands, promoting hair growth, and nourishing dry scalp. And while the oil itself likely can't make the hair grow, it's loved for its ability to create a healthier environment on the scalp that makes for way better hair growth.
- Nourishing and strengthening for strands: "Castor oil is nourishing," says King. Nazarian concurs, saying that unlike most other oils, which can veer mostly fatty, castor oil has a nutritional makeup composed of a powerful mix of proteins, vitamins, fatty acids, and antioxidants (aka the internal workings of all the buzziest hair supplements on the market). Thus, it comes as no surprise that the oil is claimed to be a wonderful way to nurture the scalp and fragile hair follicles while simultaneously encouraging healthier, faster hair growth. For this reason, castor oil has increasingly become a key ingredient in hair products.
- Might help with hair loss: While there's no concrete scientific evidence on why castor oil is so beneficial for the hair, it's certainly a well-loved oil in the beauty industry. According to Nazarian, castor oil can in fact be useful in certain cases of hair loss. Others aren't so convinced. King, for instance, says "there are no scientific studies on this or FDA approval for use for hair growth."
- Has antimicrobial properties: When it comes to scalp care, hair and scalp expert Philip B. agrees that castor oil has antimicrobial properties that may be useful in fighting off bacterial or fungal overgrowth on the scalp, but with a caveat. "It's true that fungal overgrowth can lead to hair-damaging scalp inflammation and castor oil can help with that," he says.
- Aids in scalp flaking: For those who experience flaking as a result of dry scalp, castor oil can help. "Castor oil is known to be an effective and gentle method of cleansing the skin," Nazarian explains. "Because it's polarized, the castor oil actually attracts dirt and effectively cleanses the skin."
- Protects against breakage: The idea is that the high content of ricinoleic acid may help improve blood circulation in the scalp, which might lead to nutrition for the hair follicles, stronger strands, and less breakage. Plus, castor oil is a humectant, which means it's an excellent vehicle for locking in moisture and shine. And as we know, moisturized (aka not dry, damaged, and split-prone) hair may be more likely to grow at a healthier rate.
- Increases the absorption of other products: In addition to its efficacy for the scalp, Nazarian tells us castor oil is thought to enhance and increase the absorption of other products. If incorporated into your normal hair ritual, your other products might actually penetrate more effectively, which will only do your hair's health and growth ambition a favor in the long run. After all, a residue-filled scalp does not make for a healthy mane.
Hair Type Considerations
Castor oil is best used on those with dry or flaky scalps and brittle hair (it is an oil, so it might be overkill for use on those who already have oily hair).
There's also anecdotal evidence to suggest it can be effective on the eyelashes and eyebrows. Nazarian says that while the oil is a known irritant for many, strategically applying a very small amount to eyelashes or eyebrows may help induce regrowth through a specific, localized region. If you're concerned about getting an allergic reaction, do a test patch on a small area of your skin before applying it to these sensitive areas.
How to Use Castor Oil for Hair
- Apply sparingly: Since it is an oil, a little will go a long way—it's all about moderation and being cautious. "You want to avoid overdoing it or getting it in your eyes and other sensitive areas," Nazarian warns. That said, experts seem to agree the oil is safe enough to cautiously experiment with at home. Start out with a patch test, keep expectations realistic, and heed their advice of using a small amount during application to ensure you don't experience any adverse reactions. It's also often recommended you don't use it more than once a week.
- Use as a 20-minute treatment: To use, warm the oil in your palms before working it through the roots of your hair and brushing it out toward the ends. Leave it in for 15 to 20 minutes minimum, and then shampoo it out of your hair. You can wet your hair beforehand in order to make the oil soak in better. Do note that, for some, castor oil can be difficult to work with because of its tendency to stick. "Because castor oil is highly occlusive and a big 'coater,' if you put it directly on your hair, you will be stuck with it for days and days," explains Philip B.
How to Use Castor Oil on Eyebrows and Lashes
Many swear by using castor oil on brows and lashes to reap the same benefits as those outlined here.
- To apply castor oil to your eyelashes, make sure they're completely clean and free of makeup.
- Dip a cotton swab into a small amount of oil, close your eyes, and gently swipe the oil across your lashes, being mindful that it doesn't get in your eyes.
- Try the same technique for brows, applying the oil with a cotton swab and using a tissue to ensure it doesn't go beyond the brow line, into your eyes. As Philip B notes, it can be sticky, just as it can be on the head. "It's highly viscous, meaning it can block pores or follicles and actually shrink the oil glands," he says. Try a patch test first, before committing to overall use on the brows or lashes.
Can I leave castor oil in my hair overnight?
According to herbalist Katie Pande, overnight castor oil treatments can be great for addressing split ends. “For the ultimate restorative hair mask, blend with coconut oil and leave it on overnight to work its magic on your mane," she says.
Does castor oil stop gray hair?
There are no studies to support the use of castor oil for preventing or reversing gray hair. Indeed, there is no way to reverse gray hair: “Once the melanocyte stem cells in the bulge region of the follicle are depleted it is irreversible,” Zenovia Gabriel, MD, told us. Howard Sobel, MD, says that while there is no way to prevent going gray, managing your stress, avoiding smoking, and making sure you're getting vitamins D and B12 can help keep hair from graying prematurely.