Castor Oil for Hair Growth: What the Research Actually Says
Meta Description: Does castor oil grow hair? We look at the clinical evidence (or lack thereof) for castor oil on scalp hair, eyelashes, and eyebrows — and what it can realistically do.
Quick Answer: There are no published randomized controlled trials proving castor oil promotes hair growth in humans. It’s a good hair moisturizer and coating agent that may make hair appear thicker, but claims about actual new growth are not supported by clinical evidence.
The Hair Growth Claim
Castor oil is one of the most recommended “natural hair growth” remedies on social media. The claim is that applying castor oil to the scalp, eyelashes, or eyebrows will stimulate new hair growth, make hair thicker, and reverse thinning.
What the Evidence Shows
No clinical trials for hair growth
A 2022 systematic review by Phong et al. examining coconut, castor, and argan oil for hair found no clinical evidence supporting castor oil specifically for hair growth. The review included studies on skin of color patients and noted that while coconut oil had some evidence for treating brittle hair, castor oil’s evidence was largely absent.
No eyelash or eyebrow studies
There are zero published randomized controlled trials testing castor oil’s effect on eyelash or eyebrow growth. Every dermatologist quoted in major health outlets confirms this. The idea comes from a theoretical connection: ricinoleic acid may modulate prostaglandin pathways, and prostaglandin analogs (like bimatoprost/Latisse) are proven to grow eyelashes. But castor oil is not bimatoprost — having a tangentially related mechanism does not equal clinical proof.
What castor oil actually does for hair
Castor oil is a thick, viscous oil that physically coats the hair shaft. This can:
- Reduce moisture loss from the hair
- Add temporary shine and apparent thickness
- Smooth the cuticle and reduce frizz
- Lubricate the scalp, which may help with flaking from dryness
These are cosmetic effects, not growth effects.
Jamaican Black Castor Oil (JBCO)
JBCO is made by roasting castor beans before pressing. It has cultural significance in Caribbean hair care traditions and anecdotal support, but it has the same evidence gap as regular castor oil — no clinical trials for growth.
How to Use Castor Oil on Hair (If You Choose To)
- Apply a small amount to scalp or hair ends
- Leave on for 30 minutes to overnight
- Wash out thoroughly — castor oil is very thick and may require double-shampooing
- Mixing with a lighter oil (like jojoba or coconut) makes it easier to apply and remove
- For eyelashes/eyebrows: use a clean spoolie or cotton swab, apply a thin layer at night. Avoid getting it in your eyes.
When to See a Doctor Instead
If you’re experiencing actual hair loss or thinning, castor oil is not a treatment. Conditions like androgenetic alopecia, alopecia areata, telogen effluvium, and thyroid-related hair loss have evidence-based treatments. See a dermatologist.
The Bottom Line
Castor oil is a fine hair conditioner and moisturizer. It is not a proven hair growth treatment. If you enjoy using it as part of your hair care routine, there’s no harm in that — but adjust your expectations accordingly.
Sources:
- Phong C, et al. “Coconut, Castor, and Argan Oil for Hair in Skin of Color Patients: A Systematic Review.” J Drugs Dermatol. 2022. PMID: 35816075
- Healthline. “Castor Oil for Eyebrows.” Medically reviewed, 2018.
- StatPearls. “Castor Oil.” NCBI Bookshelf NBK551626.
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