Castor Oil for Hair Growth: What It Really Does
Castor oil for hair growth is one of the most searched natural hair remedies in the UK, and the honest answer is that no clinical trial has shown castor oil makes hair grow faster or thicker from the follicle. What castor oil demonstrably does is coat the fibre, hold moisture in and cut breakage, so you keep more of the length you were already growing. That retention effect is real, it is why so many people swear by the oil, and it is the effect this guide shows you how to get safely, with or without rosemary alongside it.
Our hair and body oil
Camellia & Black Castor Hair & Body Oil, £24.95. Black castor oil thinned with lighter camellia oil, so dry lengths get the hydration and shine without the sticky, hard to rinse texture of neat castor oil.
Castor oil for hair growth works on the hair you already have rather than on the follicle. Castor oil is roughly 90 percent ricinoleic acid, a thick humectant fatty acid that lubricates the strand, slows water loss and reduces the friction that snaps hair during combing and styling. Less breakage means more retained length, which looks like faster growth. No peer reviewed trial has measured a growth effect, so use it as a conditioning oil and judge it over three to six months.
Key takeaways
- Castor oil has no credible clinical evidence for growing hair. It has very good evidence for being a heavy, effective conditioning oil that reduces breakage.
- Hair grows at roughly a centimetre a month from the follicle. Castor oil cannot speed that up, but it can stop you losing the centimetre you grew.
- Castor oil is extremely thick and sticky. Thin it with a lighter oil, use small amounts, and never pile it on and scrub, because acute hair felting is a documented risk.
- Rosemary essential oil is a reasonable scalp partner with modest research behind it, used at 3 to 5 drops per tablespoon of carrier and never neat.
- Patch test 24 hours before the first full application, and stop if your scalp reacts.
- Diffuse, heavy shedding is a blood test and GP conversation, not an oil question.
Does castor oil for hair growth actually work?
Castor oil for hair growth does not work in the way the phrase implies, because no randomised trial has ever shown castor oil increasing hair count, density or growth rate. What the oil does well is mechanical: it coats the hair, holds moisture in, adds slip and shine, and reduces the friction that causes breakage during combing and styling. People who report length gains are almost always seeing the result of less breakage.
The reason this matters is that breakage is invisible until you measure it. If your hair grows a centimetre a month and snaps half a centimetre a month at the ends, you see very little progress and conclude it is not growing. Cut the breakage and the same growth rate suddenly shows. That is the whole castor oil effect, and it is a worthwhile one for dry, coarse, curly, coily or high porosity hair where the ends are chronically fragile.
The chemistry supports the conditioning story rather than a growth story. Castor oil is made up largely of ricinoleic acid, an unusual hydroxy fatty acid that gives the oil its thickness and its ability to cling to the fibre. That is useful on a strand. There is no good evidence it does anything at the follicle, and the widespread belief that it does comes from anecdote and marketing rather than research. For the wider picture on natural ingredients with actual trial data, see our guide to what the evidence says about rosemary oil.
Is castor oil helping hair loss, hair shedding or hair breakage?
Castor oil helps hair breakage, has no effect on hair shedding, and does not act on hair loss, and those three problems need different responses, so it is worth being precise before you reach for a bottle.
- Hair loss is follicular. The follicle miniaturises and produces progressively finer hairs, as in pattern thinning at the parting or temples, or stops producing altogether, as in patchy alopecia. No oil acts here. Pattern thinning is a GP or dermatologist conversation.
- Hair shedding is a hair cycle event, where many follicles rest at once and release hairs about three months after a trigger such as illness, childbirth, a crash diet or stress. Oils do not address the trigger. Blood tests and time do. See what causes telogen effluvium.
- Hair breakage is damage to the fibre itself from heat, bleach, friction and tension. The strand snaps part way along, leaving short uneven pieces with no bulb. This is squarely where castor oil earns its place, and it is where most people using it see a genuine difference.
A quick test: gather the hairs from one wash. Full length hairs with a small pale bulb at the root are shedding. Short, blunt pieces of uneven length with no bulb are breakage. Smooth defined bald patches, or a parting that keeps widening, are a GP conversation and not a reason to buy more oil.
Which castor oil should you buy for your hair?
Buy a cold pressed castor oil labelled with the INCI name Ricinus Communis Seed Oil, in a dark glass bottle, and regard the rest of the label as marketing. Cold pressing keeps the oil pale, nearly odourless and chemically unchanged, which is what you want for a product that sits on skin and hair for hours.
| Type | How it is made | What that means in use |
|---|---|---|
| Cold pressed castor oil | Seeds pressed without heat, then filtered | Pale, thick, mild smell. The default choice for scalp and lengths |
| Jamaican black castor oil | Seeds roasted and boiled, ash left in | Dark, slightly smoky, a long standing staple in afro hair care. Same ricinoleic acid, no proven extra benefit |
| Castor oil blends | Castor thinned with lighter oils such as camellia, argan or jojoba | Spreads and rinses out far more easily. Best for fine hair and for anyone who found neat castor oil too heavy |
Two label points are worth checking. First, that castor oil is actually the main ingredient rather than a few drops in a mineral oil base. Second, that there is no added fragrance if your scalp is reactive, because fragrance is the most common cause of a scalp reaction to a hair oil. Our own Camellia & Black Castor Hair & Body Oil sits in the blend category, pairing black castor with camellia oil so it spreads on the lengths and smooths hair before a blow dry without the stickiness.
How do you use castor oil for hair growth at home?
Use castor oil for hair growth routines as a pre wash conditioning oil on the lengths, once or twice a week, thinned with a lighter oil so it spreads and rinses out. There are four sensible ways to apply it, and choosing the right one for your hair type matters more than the brand.
- The ends only conditioning routine. The best default and the breakage focused use. Warm a little between the palms and work it through the bottom third of the hair only, avoiding the roots. Leave 30 minutes before washing. This is the version most people benefit from most.
- The pre wash scalp application. Part hair in sections, apply a small amount along the partings with a dropper or fingertips, massage for two to three minutes, leave for 30 minutes to an hour, then shampoo out. Once a week is plenty. Skip this version if your scalp is oily or flaky.
- The overnight application, used with caution. Effective but messy, and this is where castor oil causes trouble. Use a genuinely small amount, dilute it well, cover with a silk scarf or an old pillowcase, and never sleep on it night after night without washing thoroughly in between.
- The blow dry smoothing drop. One or two drops of a castor blend on damp lengths before drying adds slip and shine and tames frizz. This is the everyday version and the one a blend is designed for.
Castor oil is thick enough that it benefits from being thinned. A lighter carrier at a ratio of one to two parts carrier to one part castor makes it spread, rinse out and behave on finer hair. Jojoba, almond, coconut and argan oil all work, and if you are weighing castor against other heavy oils, our guide to batana oil compares them honestly.
Should you add rosemary oil to castor oil?
Adding rosemary essential oil to castor oil is reasonable if you want a scalp ingredient with some research behind it, provided you dilute it properly, because rosemary is the only half of the pairing with any trial evidence for pattern thinning. A small randomised trial published in 2015 followed people with androgenetic alopecia for six months and reported an increase in hair count in the rosemary group by the six month mark, with less scalp itching reported than in the comparison group. A 2024 review of natural options reached a similar conclusion: promising, and still thin.
Two honest caveats. It is one small study, not a body of evidence, and it has not been replicated at scale. And the folklore about rosemary reversing grey hair remains exactly that, with no evidence behind it. Taken as a plausible, low cost scalp ingredient with modest support, rosemary is a sensible addition. Taken as a proven answer to thinning, it is oversold.
| Component | Amount | Why |
|---|---|---|
| Castor oil | 1 tablespoon | The conditioning base, for slip and moisture retention |
| A lighter carrier oil | 1 to 2 tablespoons | Thins the castor so it spreads and rinses out. Jojoba, argan, almond or coconut all work |
| Rosemary essential oil | 3 to 5 drops per tablespoon of total oil | Roughly a 1 to 2 percent dilution, the standard safe range for leave on scalp use |
Mix in a small dark glass bottle, shake before each use, and store somewhere cool and dark. Make small batches, since a blend containing carrier oils will eventually go rancid. Never apply rosemary essential oil neat to the scalp.
Who benefits most, and who should skip castor oil?
Castor oil suits dry, coarse, curly, coily and high porosity hair best, and it suits fine, low porosity or oily scalped hair least, because the same thickness that protects a fragile end weighs down a fine strand and clogs an already oily scalp.
- Best suited: dry, coarse, curly, coily or high porosity hair; anyone with breakage prone ends; anyone who heat styles or colours regularly.
- Use sparingly: fine or low porosity hair, which is weighed down easily. Stick to the ends, use very little, choose a blend, and skip the overnight version.
- Scalp caution: if you have an oily scalp, dandruff or seborrhoeic dermatitis, heavy oils on the scalp can make things worse rather than better. Keep castor to the lengths.
- Check first: if you are pregnant, ask your midwife or GP before using essential oils such as rosemary. Anyone with a known sensitivity to plants in the mint family should be careful with rosemary.
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What safety rules matter with castor oil?
Most castor oil problems are avoidable with five habits, and one of them guards against a genuinely serious outcome: acute hair felting, where hair matts into an irreversible solid mass that usually has to be cut off, documented in a 2017 case report in the International Journal of Trichology after heavy castor oil use with vigorous rubbing on long hair.
- Patch test first. A small amount on the inner forearm, left 24 hours, before the first scalp or full length application.
- Respect the thickness. Dilute castor oil, use small amounts, apply in smooth downward strokes rather than scrubbing, and detangle before you wash. Long and textured hair needs the most care here.
- Never use rosemary essential oil undiluted. Neat essential oils can irritate skin and cause sensitisation that makes you reactive to the ingredient in future.
- Wash it out properly. Apply shampoo to oily hair before adding water, which lifts oil far more effectively than shampooing already wet hair. Two washes are normal after a heavy application.
- Stop if your scalp reacts. Redness, itching or bumps mean stop, not persevere. Keep oil away from the eyes and store it out of reach of children.
What should you realistically expect, and when?
Expect slip, shine and fewer broken hairs within the first few weeks, and expect nothing measurable at the follicle at any point, because castor oil has not been shown to change the hair cycle and hair grows at roughly a centimetre a month regardless of what you put on it. Judge retention at three months at the earliest and six months for a fair verdict, and photograph a stretched section from the same spot in the same light rather than trusting the mirror.
If nothing has changed at six months, it is reasonable to conclude castor oil is not your answer and to look at heat, tension and blood tests instead. If your shedding is heavy or diffuse, see a GP before you buy another bottle. Watermans sells cosmetic hair care and does not run clinics, so anything medical belongs with your own healthcare team. If your question is about products or a routine rather than a medical one, you can talk to Gail Waterman, our co-founder, as an AI avatar on the Watermans homepage.
Camellia & Black Castor Hair & Body Oil, £24.95
If you would rather not blend your own, this pairs black castor with lighter camellia oil, so you get the conditioning benefit without the sticky texture of neat castor oil. For shine, slip and reduced breakage on the lengths, and a smoother blow dry.
Condition Me® Hair Growth Conditioner, £14.95
The everyday anti breakage step on the days you are not oiling. Shea butter, glycerin and hydrolysed lupine protein give the slip that stops detangling snapping fragile ends, which is the same job castor oil does, in a rinse out form.
Grow Me® Hair Growth Shampoo, £14.95
A sulphate free shampoo with rosemary, biotin and caffeine, useful for washing an oil application out without stripping the hair, and for keeping rosemary in the routine on the days you are not oiling. Vegan and made in the UK.
Please note: Watermans products are 100% cosmetic and do not treat medical hair loss. Individual results may vary.
What are the frequently asked questions about castor oil for hair growth?
Does castor oil grow hair?
There is no meaningful clinical evidence that it does. What it does well is reduce breakage, which often looks like growth because you keep more of the length you were already growing. That is a genuine benefit, just not the one it is usually sold on.
How often should I use castor oil for hair growth?
Once or twice a week on the lengths is plenty, and once a week at most on the scalp. More often tends to leave residue and can irritate an oily or flaky scalp. A couple of drops of a castor blend before a blow dry can be used more freely.
Can I leave castor oil in overnight?
You can, with care. Use a small, well diluted amount, protect your bedding, and wash it out thoroughly in the morning. Do not do it night after night, and be especially careful with long or textured hair, where heavy castor oil is associated with severe matting.
Is Jamaican black castor oil better for hair growth?
No evidence says so. Jamaican black castor oil is made from roasted seeds with the ash left in, which gives it the dark colour and smoky smell. The active fatty acid, ricinoleic acid, is the same as in cold pressed castor oil. Choose whichever texture and smell you prefer.
Can I mix rosemary and castor oil together?
Yes, and they complement each other well. Add 3 to 5 drops of rosemary essential oil per tablespoon of oil, and thin the castor with a lighter carrier so the blend spreads and rinses out. Never add rosemary essential oil to hair without a carrier.
Will castor oil make my hair greasy?
It will if you use too much, especially on fine hair. Start with less than you think you need, keep it to the ends if your hair is fine, choose a blend over neat castor oil, and apply shampoo before water when you wash it out.
Does castor oil help with hair shedding?
No. Shedding is a hair cycle event triggered by illness, childbirth, stress or low iron, and an oil on the lengths does not reach the cause. If you are losing full length hairs with a pale bulb in handfuls, ask your GP about blood tests rather than buying oil.
Is castor oil safe during pregnancy?
Castor oil applied to the hair is generally regarded as low risk, but check with your midwife or GP before using any essential oils such as rosemary alongside it. Advice on essential oils in pregnancy varies, and it is a simple question to ask at your next appointment.
Sources and references
- Castor Oil, The Culprit of Acute Hair Felting, International Journal of Trichology, 2017, on the matting risk described in the safety section.
- Panahi and colleagues, Skinmed, 2015, the six month randomised trial of rosemary oil in androgenetic alopecia referred to above.
- An Overview of Commonly Used Natural Alternatives for Androgenetic Alopecia, with Special Emphasis on Rosemary Oil, Clinical, Cosmetic and Investigational Dermatology, 2024, on the strength and limits of the rosemary evidence.
- NHS, Hair loss, on common causes and when to see a GP.
- British Association of Dermatologists, Telogen effluvium, on diffuse shedding and its triggers.
What is the bottom line on castor oil for hair growth?
Castor oil for hair growth is really castor oil for hair retention. It has no credible evidence for acting on the follicle, and very good practical evidence for being a heavy conditioning oil that cuts breakage, so you keep more of the centimetre a month you already grow. Thin it with a lighter oil, keep it mainly to the lengths, use it once or twice a week, patch test, and be careful with the overnight version. Add rosemary at 3 to 5 drops per tablespoon if you want the scalp ingredient with modest research behind it. Give it six months and judge by a stretched measurement rather than the mirror, and if your shedding is heavy or diffuse, see a GP rather than reaching for another bottle.
If you want the conditioning benefit without blending your own, start with our camellia and black castor hair oil on damp lengths a couple of times a week. Watermans is a UK made hair care brand with over 6.5 million bottles sold since 2012.
