Castor Oil for Hair: Benefits, Evidence and How to Use It

Castor oil for hair is best treated as a thick conditioning oil: it can coat strands and the scalp and help with dryness, but no human clinical trial has shown that it makes hair grow. A 2026 dermatology review found that traditional hair claims for castor oil have not been studied to show clinical efficacy.

That doesn't make castor oil useless, and it doesn't make it risky for most people. Below we cover what castor oil is, what the research does and doesn't say about hair growth, how Jamaican black castor oil differs, how to use it without ending up with a tangled mess, and when hair changes deserve a dermatologist instead of an oil.

What is castor oil?

Castor oil is pressed from the seeds of the Ricinus communis plant. Its standout feature is its chemistry: a 2026 narrative review in Cureus reports that ricinoleic acid makes up approximately 90% of its fatty acid content. Ricinoleic acid is what gives castor oil its unusual thickness. A case report in the International Journal of Trichology describes it as very thick and sticky in consistency, and suggests it can act as a humectant and moisturizer.

You'll see castor oil sold in two broad styles: pale, usually cold-pressed castor oil, and dark "black" castor oil, including the version sold as Jamaican black castor oil. We compare them below.

Does castor oil help hair grow? What the evidence says

This is the question most people are really asking, and the honest answer is: there's no good human evidence that it does.

The lab theory

The most-cited idea is that ricinoleic acid may block an enzyme involved in making prostaglandin D2, a compound linked to hair loss in androgenetic alopecia (pattern hair loss). The 2026 Cureus review describes this as preclinical, and says "the clinical translation of PGD2 pathway modulation in androgenetic alopecia remains uncertain." It also points out that a trial of a different drug targeting the same pathway, setipiprant, showed no efficacy.

No human trials for hair growth

The review cites no human clinical trial of castor oil for hair growth or alopecia. Its human studies covered other uses, such as under-eye pigmentation and wound care. The authors conclude that further investigation is needed before castor oil-based treatments for pattern hair loss can be established. The 2017 case report authors went further, writing that applying hair oils alone will not help hair growth and that there were no studies on castor oil's benefits for hair growth at the time.

What dermatologists caution

The American Academy of Dermatology lists "alopecia hair growth oil" among products that promise regrowth, advises caution, and recommends checking with a dermatologist before trying any hair loss product or home remedy.

What castor oil can realistically do for hair and scalp

Set growth aside, and castor oil still has a place as a conditioning oil:

• Moisture. The 2026 review describes castor oil as a moisturizing agent and carrier oil, and notes that in a wound-dressing setting it can decrease the loss of water vapor.
• A gentle option on skin. In one study the review cites, a castor oil cleanser preserved the skin barrier better than a walnut shell cleanser in people with atopic skin.
• Shine and protection. The 2017 case report authors suggest oils are better thought of as protecting the hair shaft than growing hair.

The AAD's healthy hair tips are a useful frame. They suggest concentrating shampoo on the scalp, applying conditioner along the full length of dry or curly hair but only to the ends of fine or straight hair, and, if you see flakes, checking that your conditioner, oil or scalp moisturizer suits your hair type.

Jamaican black castor oil vs. regular castor oil

Jamaican black castor oil (JBCO) is the dark castor oil sold under that name; sellers describe a traditional process that roasts the seeds before the oil is extracted. We searched for peer-reviewed research describing or testing JBCO and found none, and the 2026 dermatology review does not mention it. So there is no published evidence that JBCO is better, or worse, for hair than clear castor oil.

Note that "black castor oil" is not always Jamaican. The Katari oil we carry, for example, is described by the brand as a cold-pressed, unrefined black castor oil and a Mediterranean staple. Choose based on feel and smell, not promises.

How to use castor oil for hair

1. Patch-test first. The 2026 review lists contact dermatitis as castor oil's most common side effect and identifies ricinoleic acid as the primary sensitizing component. The AAD suggests testing a new product on the inside of your arm twice daily for seven to 10 days.
2. Use a small amount. Castor oil's thickness is part of why it has been linked to matting. A few drops, or a blend with a thinner oil, goes a long way.
3. Work in sections. Apply to the scalp or to dry ends, depending on your goal, and smooth it along strands rather than piling it on.
4. Massage gently. Use your fingertips, not your nails, and avoid twisting or rubbing long hair into a knot.
5. Shampoo it out. Focus shampoo on the scalp, as the AAD recommends. You may need two washes to remove a heavy oil.
6. Detangle carefully. The AAD suggests a wide-tooth comb on wet hair and wrapping hair in a towel or T-shirt instead of rubbing it dry.

For brows and lashes, keep oil out of your eyes. The dermatology review did not assess castor oil for eyelash use, so there is no research-backed routine to follow.

Castor oil for different hair types

Dry, curly or coily hair

The AAD suggests that dry or curly hair benefits from conditioning along its full length. If you like the feel of castor oil, a light coat on the lengths, followed by a thorough wash, fits that approach.

Fine or straight hair

The AAD recommends keeping conditioner on the ends of fine or straight hair. A heavy oil can weigh it down, so use very little, or choose a lighter oil.

Thinning edges and the scalp

If your edges or hairline are thinning, the AAD advises avoiding tight styles, dry heat and harsh chemicals that irritate the scalp, and seeing a board-certified dermatologist early. For some types of hair loss, delay allows the loss to progress.

What to look for when buying castor oil

• Single ingredient or blend. Check whether the bottle is just castor seed oil or a mix with other oils, herbs or fragrance.
• Fragrance. If your scalp is sensitive, skip added fragrance and essential oils.
• Texture. Black and clear castor oils are both thick. If you have fine hair, a blend with a lighter oil may be easier to use.
• Honest labeling. Be wary of growth promises; the research doesn't support them yet.

Shop our castor oil collection or the wider hair collection. Listings for context:

• Katari Black Castor Oil for Hair & Brows is a cold-pressed, unrefined black castor oil. The brand describes it as a very rich, viscous oil that is slow to absorb, and suggests it as a pre-shampoo treatment, scalp massage oil or overnight hair mask.
• Come Alive Herbals Castor Oil is positioned by the brand as a multi-use oil for skin and hair, drawing on Ayurvedic tradition.
• Katari Henna Oil for Dry Hair & Scalp is a lighter option to consider; the brand describes it as a medium-weight, non-staining oil that absorbs within one to two minutes.

Who should skip castor oil, or be careful

• People with known castor oil or fragrance allergies. Contact dermatitis is the most commonly reported reaction, and the review notes that reactions were mostly reported with non-hydrogenated castor oil, the kind sold for hair.
• Anyone with long, fine or easily tangled hair. Acute hair felting is rare, but the case report describes a 20-year-old whose hair matted into a hard mass within a day of using coconut oil and castor oil, her first time with castor oil, during a hair wash. Matted hair of this kind cannot be untangled and had to be cut off. The authors linked it to castor oil's high viscosity and long hair.
• Anyone with active hair loss. See a dermatologist. Patchy loss, scalp pain or scarring need a diagnosis, not an oil.
• Anyone pregnant or managing a scalp condition should check with their doctor or dermatologist before starting new products.

Using castor oil on your beard too? Our beard balm guide explains how oils, butters and balms differ. And if you're curious about oils for skin, see face oil for dry skin.

FAQ

Does castor oil really make hair grow?

There's no human clinical evidence that it does. A 2026 dermatology review found no human trials of castor oil for hair growth and described the main theory, that ricinoleic acid may affect prostaglandin D2, as preclinical. Castor oil can condition hair, but for real hair loss the AAD recommends seeing a dermatologist before trying home remedies.

Is Jamaican black castor oil better than regular castor oil?

We couldn't find any published research comparing the two, and the 2026 dermatology review on castor oil doesn't mention Jamaican black castor oil at all. Both are thick oils based on castor seeds. Choose the one whose scent, color and texture you prefer, and ignore claims that one grows hair faster.

How often should you put castor oil in your hair?

There's no research-backed schedule. Start with occasional use, such as a pre-shampoo treatment, and see how your hair and scalp respond. Use only a small amount, wash it out thoroughly, and stop if you notice itching, redness or new tangling. Follow the directions on your product's label.

Can castor oil damage your hair?

Rarely. The main risks reported are allergic or irritant reactions on the skin and acute hair felting, a sudden, irreversible matting described in a 2017 case report after castor oil was applied to long hair. Using small amounts, working in sections and detangling gently can reduce tangling problems.

Can I leave castor oil in my hair overnight?

Some brands suggest overnight masks, but there's no research showing longer contact gives better results. If you try it, use a small amount, protect your pillowcase, and wash it out in the morning, focusing shampoo on the scalp. If your scalp becomes itchy or irritated, rinse it off and stop.

Does castor oil help eyebrows and eyelashes?

We didn't find good evidence that it does. The 2026 dermatology review did not assess castor oil for eyelashes, and the AAD's hair loss guidance recommends checking with a dermatologist before trying growth remedies. If you use it on brows, apply a tiny amount with a clean spoolie and keep it away from your eyes.

Sources

• Girdler K et al. Use of Castor Oil in Dermatology: A Narrative Review. Cureus, 2026
• Maduri VR et al. "Castor Oil": The Culprit of Acute Hair Felting. International Journal of Trichology, 2017
• American Academy of Dermatology: Tips for healthy hair
• American Academy of Dermatology: Central centrifugal cicatricial alopecia self-care
• American Academy of Dermatology: How to test skin care products

This guide is general information, not medical advice. Patch-test new products and ask a dermatologist or doctor about skin or health concerns.