Last updated: March 2026 — Written by the ORVOVA team, reviewed by our dermocosmetics advisor.
Type "castor oil for hair" into Google and you will find thousands of glowing testimonials. Spectacular before/after photos. TikTok videos with millions of views. Castor oil is supposedly the secret to hair growth, the miracle cure for hair loss, the natural solution Big Pharma doesn't want you to know about.
Except that when you look at what the science actually says... it is far more nuanced. And that nuance is exactly what is missing from 99% of the content you will find online.
This article takes the honest route. We will break down the real evidence, explain why castor oil has some interesting properties, why it cannot do what people claim, and which alternatives are actually backed by research.
Contents
The castor oil hype: where does it come from?
Castor oil (Ricinus communis) is extracted from the seeds of the castor plant, a tropical plant. Its use goes back to ancient Egypt — Cleopatra is said to have used it on her eyelashes. But today's hype comes mainly from three factors.
Social media
TikTok and Instagram have turned castor oil into a viral phenomenon. The #castoroil hashtag has racked up billions of views. Short videos leave no room for nuance: show a before/after, credit castor oil for the result, and that's it.
The problem: these before/afters don't control for any variables. A new shampoo, stopping a medication, the end of a stressful period, a change in diet — any of these factors could explain the improvement.
Ricinoleic acid
Castor oil contains about 90% ricinoleic acid, a hydroxylated fatty acid that is unique in the plant world. This acid has documented anti-inflammatory properties (Vieira et al., 2000, Mediators of Inflammation) and increases the production of prostaglandin E2 (PGE2).
PGE2 plays a role in the hair cycle. That indirect mechanism is what led to the hypothesis that "castor oil makes hair grow". An appealing hypothesis... but one that has never been directly demonstrated.
Price and availability
At 5-10 euros for a 100 mL bottle, castor oil is affordable for everyone. That is a powerful argument in a market where anti hair loss treatments often cost 30 to 80 euros. The "hope for the price" ratio is unbeatable.
[Image: A bottle of castor oil and castor seeds — the star ingredient of social media]
What the science says (honestly)
Here is the most important point in this article: there is no published clinical study showing that castor oil makes hair grow. Zero. None.
This is not an opinion. It is a fact you can check in scientific databases (PubMed, Cochrane Library, Google Scholar). As of March 2026, no randomised controlled trial has assessed the effect of castor oil on human hair growth.
What is proven
- Anti-inflammatory properties: ricinoleic acid reduces inflammation (Vieira et al., 2000). A less inflamed scalp is more favourable to hair growth. But "favourable" is not "causal".
- Emollient properties: castor oil is an excellent moisturiser. It forms a protective film on the hair shaft that reduces breakage and makes hair look thicker. But making hair look thicker is not the same thing as growing new hair.
- Effect on PGE2: prostaglandin E2 is involved in the hair cycle. But a link between applying castor oil topically and a significant increase in PGE2 at the follicle has never been shown in humans.
What is not proven
- That castor oil stimulates the growth of new hair
- That castor oil slows down hair loss
- That castor oil reactivates dormant follicles
- That castor oil inhibits DHT (dihydrotestosterone)
The confirmation bias trap
So why do so many people swear that castor oil made their hair grow? There are several explanations:
- Massage: applying castor oil means massaging your scalp. And massage alone stimulates microcirculation and hair thickness (Japanese study, Eplasty, 2016). The benefit could come from the gesture, not the product.
- Hydration: moisturised, protected hair breaks less. Less breakage = more length retained. That is not extra "growth", it is length retention.
- Paying attention to your hair: when you start a "treatment", you also pay more attention to your diet, handle your hair less and use less heat. All of these factors contribute to the improvement.
[Image: What science proves vs what social media claims about castor oil]
Also see our article on scalp massage.
How to use it if you want to try it
Castor oil is not a bad product. It has real cosmetic qualities. If you would like to add it to your hair routine, here is how to get the most out of it — without unrealistic expectations.
As a hair oil treatment (once a week)
Castor oil is very thick and sticky. Used on its own, it is hard to apply and a pain to rinse out. The best approach:
- Mix 1/3 castor oil + 2/3 jojoba oil (or fractionated coconut oil)
- Apply to the scalp section by section
- Massage for 3 to 5 minutes with your fingertips
- Leave on for 1 to 2 hours (or overnight with a towel)
- Wash with a double shampoo (castor oil is very hard to remove in a single wash)
What it really does: moisturises the scalp, protects the hair fibre, reduces breakage, makes hair feel thicker (a cosmetic effect, not a structural one).
For lashes and brows
This is probably the most relevant use for castor oil. Brushed onto lashes and brows every evening, it conditions them, reduces breakage and makes them look fuller. Here too, the effect is mainly cosmetic (protection + hydration), but it is visibly noticeable.
What NOT to do
- Apply it every day: castor oil is too heavy for daily use. It can clog follicles and have the opposite effect (folliculitis).
- Use it as your only anti hair loss treatment: if you have active hair loss, castor oil alone won't solve the problem. It is a cosmetic treatment, not a medical one.
- Leave it on for more than 12 hours: beyond that, the risk of clogged follicles increases.
More effective alternatives (with evidence)
If your real goal is to support regrowth and slow down hair loss, here are the actives that have published clinical data behind them.
Redensyl: +17% hairs in the growth phase
Developed by Induchem (Switzerland), Redensyl is a complex that reactivates the stem cells of the hair follicle. The reference clinical trial (2014, double-blind, 26 volunteers) showed +17% hairs in the anagen phase and -17% in the telogen phase after 84 days.
That is exactly the kind of evidence castor oil lacks: a controlled, double-blind trial with objective trichogram measurements.
Redensyl acts on the ORSc (Outer Root Sheath cells) — the follicle's stem cells — to steer them back into the growth phase. No rebound effect when you stop, no systemic side effects.
Rosemary essential oil: comparable to Minoxidil 2% in one study
The Panahi et al. study (2015, SKINmed) compared rosemary with Minoxidil 2% over 6 months. Result: comparable effectiveness on hair density, with less irritation in the rosemary group.
The mechanism is twofold: stimulating microcirculation AND inhibiting 5-alpha reductase (the enzyme that produces the DHT responsible for follicle miniaturisation).
Unlike castor oil, rosemary has a randomised controlled clinical study behind it. It is a natural active with a real scientific record.
Aminexil: protecting the hair's anchoring
Aminexil prevents the collagen around the hair root from hardening (perifollicular fibrosis). When this sheath stiffens, the hair falls out prematurely. Aminexil keeps the anchoring supple. Documented reduction in hair shedding of 10 to 15% in 6 weeks (Kligman, 2003).
Anagain: restarting the growth cycle
Derived from organic peas, Anagain stimulates FGF7 (Fibroblast Growth Factor 7) to wake up dormant follicles. +78% improvement in the anagen/telogen ratio in 12 weeks (Mibelle Biochemistry, 2012).
A well-documented alternative
ORVOVA Hair Growth Serum Roll-On
A concentrated formula with 4 actives backed by published studies: 3% Rosemary, 3% Redensyl, 2% Aminexil, 2% Anagain. Each active has its own study. Roll-on applicator to target the scalp with no waste. Silicone-free, castor-oil-free.
[Image: Comparison table of evidence levels — castor oil vs Redensyl, rosemary, Aminexil]
Also worth reading: our complete guide on how to strengthen keratin naturally.
FAQ
Does castor oil really make your hair grow?
There is no clinical study showing that castor oil stimulates the growth of new hair. Its emollient properties protect the hair shaft and reduce breakage, which can give the impression of longer hair. Its anti-inflammatory properties (ricinoleic acid) are documented, but a direct link to hair growth has never been established in humans. For a demonstrated effect on growth, actives such as Redensyl (+17% hairs in the growth phase in 84 days) or rosemary (comparable to Minoxidil 2% over 6 months) have clinical evidence.
Can you use castor oil on your hair every day?
No, it is not recommended. Castor oil is very thick and sticky. Used daily, it can clog hair follicles and cause folliculitis (inflamed follicles). A weekly oil treatment followed by a double shampoo is the ideal frequency. If you are looking for a daily hair care product, a lightweight serum with actives such as rosemary or Redensyl is a better fit.
What is the difference between castor oil and a hair growth serum?
Castor oil is a cosmetic treatment that moisturises and protects the hair fibre. A hair growth serum contains actives that act directly on the hair follicle to restart the growth cycle (Redensyl on stem cells, rosemary on microcirculation and DHT, Aminexil on anchoring). The fundamental difference is the level of evidence: serums formulated with documented actives have clinical studies behind them, castor oil has none on regrowth.
Can castor oil cause hair loss?
Indirectly, yes. A phenomenon called "hair felting" has been documented: very sticky castor oil can tangle hair severely, causing breakage and hair being pulled out when detangling. On top of that, applying it too often or too thickly can clog follicles and cause folliculitis, which in turn can make hair loss worse. To avoid these problems: always dilute castor oil, leave it on for 12 hours maximum, and rinse thoroughly.
Which natural alternatives are proven for hair growth?
Three natural or bio-inspired actives have published clinical studies. Rosemary (Panahi et al., 2015) showed effectiveness comparable to Minoxidil 2% after 6 months. Redensyl (Induchem, 2014) showed +17% hairs in the growth phase in 84 days by reactivating follicle stem cells. Anagain (Mibelle Biochemistry, 2012), derived from organic peas, improves the growth ratio by +78% in 12 weeks. Unlike castor oil, these actives directly target the mechanisms of hair loss.
Conclusion
Castor oil is neither a miracle nor a scam. It is a good cosmetic treatment — moisturising, protective, affordable — that social media has promoted to the rank of "anti hair loss treatment" without any scientific evidence to back up that claim.
If you use it alongside a balanced hair routine, as a weekly oil treatment, it can improve the look and feel of your hair. That is already something.
But if your goal is to slow down active hair loss and support regrowth, turn to actives whose effectiveness is documented by clinical trials: Redensyl, rosemary, Aminexil and Anagain. It is not a choice between "natural" and "chemical" — it is a choice between "documented" and "assumed".
Your hair deserves better than hypotheses. It deserves evidence.
