How To Apply Castor Oil To Hair: Mistakes That Slow Growth
Castor oil is the most dramatic thing in your bathroom cabinet.
One person puts it on and gets glossy, bouncy lengths. Another puts on the exact same oil and ends up with a scalp that feels laminated, and a rinse that takes three shampoos and a lot of muttering.
Same bottle. Very different outcome.
If you’re wondering how to put castor oil in hair without turning it into a project, here’s the good news: the difference is almost never the oil. It’s the technique.
How much you use. Where it goes. How long it stays. And, above all, how you get it out (this is the bit nobody warns you about).
You’ve probably also seen the castor oil hair growth before and after photos. I’ll get to those, because the story behind them is more interesting than the caption suggests.
First, let’s get the basics right.
I’m Patri Hernández, a certified organic skincare formulator and dermocosmetic technician with a background in health coaching, specialising in natural skincare, plant oils and evidence-informed approaches to wellness. Castor oil is unusually thick, which is exactly why technique matters so much with it.
Some links here may be affiliate links, which means I may earn a small commission if you buy through them, at no extra cost to you. That never influences what I recommend, and I only point you to things I believe may genuinely be useful.
What you get from doing this properly
Let’s be concrete about what’s in it for you.
- No more guessing: you’ll know how much to use for your hair length, so you stop wasting oil.
- Easier washing: a wash-out method that usually takes one or two shampoos instead of four.
- Less buildup and matting: the two things that put most people off castor oil for good.
- More length kept: less breakage means the hair you grow actually stays on your head.
- Realistic expectations: so you don’t spend six months chasing a result the evidence doesn’t promise.
Here’s the reframe that changes everything: technique mistakes don’t slow your follicles. They cost you length through breakage, buildup and tangles. The result looks the same, but the cause is different.
Choose the right castor oil first
Look for pure castor oil. On a label, it appears as Ricinus communis seed oil.
Regular castor oil is pale and fairly mild. Jamaican black castor oil is made from roasted beans, so it is darker and smells smoky.
The ash left from roasting is said to make the oil more alkaline. Brands often say that this helps the oil soak in. I’m not aware of independent testing that backs this up, so I’d treat it as a traditional claim, not a proven one.
As a formulator, my practical advice is simple: if your scalp is sensitive, start with the paler oil and patch test the darker one more carefully.
Good to know: castor beans contain ricin, but ricin does not end up in the oil. The Cosmetic Ingredient Review panel, which assesses cosmetic ingredient safety, concluded that castor oil is safe as used in cosmetics (PubMed).
Please don’t pound castor beans at home, though. The beans themselves are poisonous if swallowed.
Not a TikTok invention: the Ebers Papyrus, an Egyptian medical scroll from around 1550 BC, suggests pounding castor beans, soaking the paste in oil and massaging it into the scalp for hair loss (Biblical Archaeology Society).
Three and a half thousand years later, we are still trying it.
How much castor oil to use
This is where most people go wrong. Castor oil is far thicker than other plant oils, so less really is more.
| Hair length | Pure castor oil | Blended (recommended) |
|---|---|---|
| Short or fine | ½ teaspoon | 1 teaspoon |
| Shoulder length | 1 teaspoon | 2 teaspoons |
| Long or thick | 2 teaspoons | 1 tablespoon |
These are starting points, not rules. You can always add a little more. You can’t take it back out of dry hair.
My formulator’s advice is to blend it. Mix castor oil 1:1 or 1:2 with a lighter oil such as jojoba oil or sweet almond oil.
You keep the slip and gloss, and you lose some of the stickiness that makes it so hard to wash out.
How to apply castor oil: scalp versus lengths
These are two different jobs, so treat them differently.
On the scalp
- Section dry hair into four parts.
- Warm the oil between your fingertips. Please don’t microwave it.
- Apply along the partings with your fingertips, not straight from the bottle.
- Massage for a few minutes in small circles.
Aim for a thin film, not a puddle. A scalp swimming in oil is more likely to feel itchy and congested than nourished.
Wow moment: the massage may matter more than the oil.
In a small Japanese study, nine men had four minutes of standardised scalp massage a day for 24 weeks. Their hair thickness increased from 0.085 mm to 0.092 mm (PubMed).
It was nine men, there was no oil involved, and it measured thickness, not new hair. But it’s a good reason not to skip the massage.
On the lengths
Use a tiny amount, and only on the mid-lengths and ends. These are the oldest and driest parts of your hair.
Smooth it on with your palms rather than raking it through.
Fine or low-porosity hair? Skip the lengths, or use a very diluted blend. Castor oil is heavy enough to flatten fine hair.
Dry hair or damp hair?
Dry hair gives you the most control. The oil stays where you put it and spreads evenly.
Slightly damp hair is fine if you want a lighter coating. On very wet hair, the oil beads up and goes on patchy.
How long to leave castor oil on
| Time | What to expect |
|---|---|
| 30 minutes to 2 hours | Plenty for conditioning. Easiest to wash out. |
| Overnight | More mess, more buildup, harder wash-out. Not more benefit that I’m aware of. |
There’s no evidence I know of that a longer soak does anything extra. Overnight is where people tend to get into trouble.
If you do leave it on overnight, tie your hair up loosely and protect your pillowcase.
How to wash castor oil out without damaging your hair
Oil and water don’t mix. Splashing wet hair with shampoo does very little.
- Shampoo first, on dry hair. Put a generous amount straight onto the oiled hair and scalp before any water touches it.
- Massage for a minute or two. The shampoo needs time to bind to the oil.
- Add a little lukewarm water and keep working it into a lather.
- Rinse thoroughly. Shampoo again if it still feels slick.
- Condition the lengths only.
Be gentle. Rough handling is how oiled hair turns into a tangle, so don’t scrub or pile long hair into a knot on top of your head.
The rare risk worth knowing about: a 2017 case report in the International Journal of Trichology described a woman who used castor oil and coconut oil on long hair for the first time. She washed it out with warm water, and her whole scalp of hair matted so badly that she was advised to cut it off (PMC).
The authors suggested the oil’s thickness, the long hair and the warm water all played a part. It’s a single reported case, so it’s rare. It’s still a useful reminder of why the wash-out method matters.
Common castor oil mistakes that cost you length
- Using too much. By far the most common one.
- Putting it on neat, on long or fine hair. Blend it.
- Wetting hair before shampooing. Shampoo goes on first.
- Leaving it on overnight, every night. Buildup follows.
- Oiling too often. Once a week or fortnight is plenty for most people.
- Skipping the patch test. Reactions to castor oil are rare, but they are documented.
- Expecting overnight results. More on that next.
What results can you realistically expect?
This is where I’ll be direct, because a lot of what’s online isn’t.
What the evidence says
- A 2022 systematic review of 22 studies on coconut, castor and argan oil found weaker evidence that castor oil improves hair lustre, and no strong evidence that it grows hair (Journal of Drugs in Dermatology).
- A 2026 narrative review of castor oil in dermatology reached a similar place: promising for hair quality, thin on proof for growth (Cureus).
- Castor oil is about 90% ricinoleic acid. In the lab, that acid has been linked to prostaglandin pathways involved in hair growth. That’s an interesting mechanism, not proof that it works on a human scalp.
What’s more plausible
- Shinier, smoother-looking hair, because the oil coats the strand.
- Less friction and breakage, so you may keep more length.
- A softer feel on dry ends.
Why the before and after photos fool us: scalp hair grows about half an inch a month, give or take. Dermatologist Dr Hadley King told USA Today that hair growth treatments generally work by keeping hair in its growth phase for longer, not by speeding it up (USA Today via AOL).
So what looks like faster growth is often a trim, better lighting, or hair that snaps less. Hair that breaks less looks like it grows faster, even when the follicles haven’t changed.
Bloggers and content creators often present anecdotes as proof. Most don’t have the training to check the science, or the formulation background to explain why something works.
If growth is your goal
Castor oil doesn’t have good trial data for growth. Rosemary has a bit more.
A 2015 trial of 100 men with pattern hair loss compared rosemary oil with 2% minoxidil over six months. The two performed similarly, and the rosemary group reported less scalp itching (PubMed).
It was one small trial, in men only, so I’d call it encouraging, not settled. If you try it, rosemary essential oil must always be diluted in a carrier oil, and it isn’t suitable in pregnancy.
My guide on growing hair faster with castor oil goes into that side in more detail. And if you have curls, andiroba oil for curls is a lighter option worth a look.
Who castor oil suits (and who should be careful)
- Usually a good match: thick, coarse, dry or high-porosity hair.
- Be careful: fine, thin or low-porosity hair. It weighs it down quickly.
- Patch test first: put a small amount on the inside of your elbow and wait 24 hours.
- Keep it out of your eyes.
- Pregnant or breastfeeding? Topical use is generally considered low risk, but check with your midwife or doctor.
See a doctor or dermatologist if you notice sudden shedding, patchy hair loss, a painful or inflamed scalp, or thinning that keeps progressing. No oil fixes an underlying cause.
FAQ
How often should I use castor oil on my hair?
Once a week or every two weeks suits most people. Fine or low-porosity hair may do better monthly.
Can I put castor oil on wet hair?
You can, but use only a small amount. Dry hair gives you far more control.
Is it safe to leave castor oil on overnight?
It isn’t dangerous for most people, but it isn’t necessary either. It raises the chance of buildup and a harder wash-out.
Why does my hair feel stiff after castor oil?
Usually too much oil, or not enough shampoo before rinsing. Wash again, then condition the lengths.
Is Jamaican black castor oil better than regular castor oil?
It’s different, not proven better. It’s darker and smokier, and its claimed extra benefits haven’t been independently tested that I know of.
Does castor oil actually grow hair?
The evidence is weak. It may improve shine and reduce breakage, which can help you keep length.
Conclusion
Castor oil is a good hair oil with an inflated reputation. Treat it as a conditioning treatment, not a growth drug.
Use less than you think. Blend it. Keep it mostly on the lengths. Leave it for an hour or two, and shampoo it out before any water touches your hair.
That’s the whole system.
References
- Final report on the safety assessment of Ricinus communis (castor) seed oil and related ingredients (Cosmetic Ingredient Review, PubMed)
- “Castor Oil”: The Culprit of Acute Hair Felting (International Journal of Trichology, PMC)
- Coconut, Castor, and Argan Oil for Hair in Skin of Color Patients: A Systematic Review (Journal of Drugs in Dermatology)
- Use of Castor Oil in Dermatology: A Narrative Review (Cureus, PMC)
- Standardized Scalp Massage Results in Increased Hair Thickness (Eplasty, PubMed)
- Rosemary oil vs minoxidil 2% for the treatment of androgenetic alopecia (Skinmed, PubMed)
Love, Patri xx
