It seems as if every other day there’s a new skin or hair ingredient en vogue that’s suddenly deemed the miracle worker we’ve been waiting for. Considering that we live in the age of TikTok and light-speed trend cycles, this isn’t necessarily surprising, but it does make us question what does and doesn’t work. For moments like this, we dive head-first into the research (and call upon the experts), to determine whether our beauty routine actually needs another step. Currently, we’re studying up on castor oil.

Believe it or not, castor oil has been used for millennia. The natural oil is believed to have properties that encourage hair growth, health, and thickness. And being that it supposedly has such an effect on hair, castor oil can be found in many hair care products, as well as brow and lash serums.

To set the record we straight—and manage expectations of the alleged miracle worker—we spoke to three experts about its hair growth potential and what we should be wary of. Below, find insights from a hair expert, cosmetic chemist, and board-certified dermatologist, and learn everything there is to know about using castor oil for your hair.

What Is Castor Oil?

Castor oil is a nutrient-dense oil extracted from pressed seeds of the castor oil plant Ricinus communis, which is mainly grown in India, South America, Africa, and China. The produced oil typically has a pale-yellow or almost colorless appearance with a subtle mild scent. It has many medicinal, household, and pharmaceutical uses and is also widely used in skincare and cosmetics for its potential healing properties.

Benefits of Castor Oil for Hair

The use of castor oil for hair dates back to 4000 BC in ancient Egypt. 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.

• Nourishingand 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.

1. To apply castor oil to your eyelashes, make sure they’re completely clean and free of makeup.
2. 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.
3. 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.