A young woman sitting in bed ties up her hair into a ponytail.
Using castor oil once or twice a week along with your regular hair care routine can help your hair and scalp retain moisture better.Lena Mirisola/Getty Images
  • Castor oil may help improve hair health and growth by boosting blood flow to your scalp.
  • Scientific evidence remains limited, but anecdotal evidence suggests castor oil does benefit hair.
  • Start by applying castor oil to your hair once or twice weekly, leaving it on for 20 to 30 minutes.
  • Visit Insider's Health Reference library for more advice.

Castor oil is a vegetable oil rich in antioxidants, vitamins, and minerals that give it anti-inflammatory and antibacterial properties. 

While it's commonly used as a laxative, it's also become a popular additive in skin and hair products, particularly as a natural way to improve hair growth.

How can castor oil promote hair growth?

"Castor oil is thought to help promote hair growth by increasing blood flow to the scalp to help lead to healthier and stronger hair; however, there is little evidence from large clinical studies to fully establish these benefits," says Marisa Garshick, MD, FAAD, a board-certified dermatologist at MDCS Dermatology. 

While more research is needed to fully establish castor oil's hair growth benefits, Garshick acknowledges that anecdotally, people have noticed improvement when using it. This is likely because it benefits the scalp and hair in ways that may help as you grow your hair.

"It is thought to be related to the fact that it's rich in vitamin E and other antioxidants. It can also be helpful for overall scalp health as it reduces inflammation and also has antibacterial and antifungal properties. It also contains omega-6 fatty acid, which is a fatty acid that may help to promote hair growth," says Garshick.

Antioxidants like vitamin E help protect against a process called oxidative stress in which healthy cells are damaged by free radicals. Oxidative stress contributes to hair loss as well as various chronic health conditions.

Some limited evidence also suggests vitamin E could help increase blood flow to the scalp, which could theoretically help improve hair growth. Evidence also supports vitamin E's anti-inflammatory and protective effects against damage from UV light.

Can it benefit hair health in other ways?

Castor oil is rich in a fatty acid called ricinoleic acid that can moisturize your skin and hair, preventing dryness and breakage.

These types of fatty acids work as humectants, which moisturize the skin and hair by drawing in moisture from the air. They can also help your skin retain moisture by creating a barrier over the outer layer of the skin.

Along with helping reduce dryness and breakage, the extra moisture can also contribute to shinier, healthier-looking hair.

Who can use castor oil? 

While castor oil is generally safe for use, it may cause allergic reactions in some including allergic contact dermatitis and skin, eye, and respiratory irritation.

Castor oil was also linked to a case of acute hair matting, a rare disorder of the scalp and hair. The sudden, severe matting of a woman's hair was documented in a case report in the International Journal of Trichology in 2017. It's worth noting, though, that this is the only known case linked to castor oil to date. Plus, the woman in the case report used a combination of castor oil, coconut oil, and water, not castor oil alone.  

As is generally recommended when trying a new skin or hair product, you may want to perform a patch test beforehand to make sure you don't have any adverse reactions.

"Apply a small amount to the inside of the forearm or back of neck and leave it on for 24 hours. Then see if you develop a reaction," says Garshick.

How to use castor oil for your hair

Want to try castor oil for hair growth or just to add some extra moisture and shine to your mane? Jennifer Korab, celebrity hair stylist and colorist and owner of Renaissance Salon and Spa, offers some advice on how to do it.

How much castor oil to use:

"It changes from person to person depending on hair texture and density. Use enough to make sure to coat the hair so you can see the shine," says Korab.

How often:

"There is no standard for how often to use it, but I recommend one to two times a week. As with anything, consistency is key to get the benefits, but make sure to not overuse," says Korab.

Leave the castor oil on your hair for 20 to 30 minutes before washing it off.

"Benefits are not going to happen overnight," says Korab, who recommends sticking with one or two weekly applications for a couple of months.

Choosing a product

The market is chock full of hair products containing castor oil, and the lack of research available makes it difficult to pinpoint the best castor oil for hair growth.

That said, keeping these tips in mind when shopping can help you choose the right product for your needs:

  • If you have allergies, check the label for other ingredients to ensure the product doesn't contain anything you're allergic to.
  • Avoid products that contain harsh ingredients that can dry the scalp and hair, such as alcohol.
  • Choose verified organic castor oil to avoid potential toxins, such as pesticides.
  •  If you find the thick consistency of castor oil hard to apply or too heavy for your hair, dilute it with a carrier oil, like olive oil or coconut oil.

Insider's takeaway

Data may be lacking on castor oil as a hair growth remedy. But that doesn't mean it won't necessarily work, and there's little harm in trying it — aside from a potential allergic reaction. 

You can try coating your hair a couple of times a week to test any potential hair growth benefits for yourself. But don't rely on castor oil alone to promote and maintain hair health. 

To prevent thinning and damage from everyday styling, Korab also recommends using a heat protectant.

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