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Botanical Index / everything about

Castor

Thick, sticky, mostly ricinoleic; nicer conditioner than grower

Ricinus communis

Castor leaves and spiky seed pods.
Illustration

The short version

Castor oil is a very thick plant oil pressed from castor seeds. It sits on the surface, softens hair, and helps seal in moisture. People also try it on brows and lashes, but growth claims are much stronger in marketing than in studies.

Family
Euphorbiaceae
Part used
Seed (pressed oil)
Comes from
Probably north-east Africa; now grown across the tropics, mostly in India

Good for?

Used as a heavy emollient and occlusive to lock in moisture and add slip. Common in hair and beard blends to soften coarse fibers and reduce friction and itch from new growth. Formulators also use castor oil in cleansers and modern gels to help lift oily makeup/sunscreen and to carry actives in controlled systems. It’s often rubbed on brows and lashes, though human evidence for thicker growth is weak.

Does it actually work?

Early days.

A few small studies on people. Interesting, not settled.

Evidence grade 3 out of 5.

“Most evidence is preclinical or formulation-focused.”

What the studies say

Most evidence is preclinical or formulation-focused. A small randomized trial tested a rosemary–castor blend on scalp hair, but it cannot isolate what castor oil did by itself. A tiny mouse study suggested castor oil alone underperformed rosemary, while a 1:1 blend trended closer to minoxidil in that model. Systematic discussions of hair oils consistently note little to no controlled human data showing castor oil increases lash or brow growth. Practical conditioning and lubrication benefits for hair and beard are plausible and supported by use in formulations, not by growth trials.

A person brushes oil onto a bold eyebrow, framed by star-shaped castor leaves.
Illustration

What's inside

  • 85–90%Ricinoleic acid (as triglycerides)Dominant fatty acid; defines the oil’s thickness and feel.
  • 2–6%Oleic acid
  • 1–5%Linoleic acid
  • 0.5–2%Stearic acid
  • 0.5–2%Palmitic acid
  • trace–2%Dihydroxystearic/related acidsLevels vary with processing; higher in hydrogenated forms.

Read this first

Properly processed cosmetic castor oil is considered safe; the raw seeds are toxic but the oil does not contain ricin after purification. Rare reactions include contact dermatitis and occasional hair felting; patch test if you’re sensitive. In scented blends, fragrance components are the usual irritants, not the carrier oil.

An expert safety panel concluded Ricinus Communis (Castor) Seed Oil and related ricinoleates are safe as used in cosmetics under current practices and concentrations.

The stories

5 in the Journal

Index Explainer · Beard

Beard oils: what’s actually in them and what they do

Beard oils are mostly light carrier oils (jojoba, argan, sometimes castor) plus fragrance; as topical emollients they soften coarse facial hair and can reduce skin inflammation and itch, but there’s little direct human evidence that they make beards thicker or grow faster. (Evidence for moisturising and anti-inflammatory effects comes mainly from lab, animal and formulation studies.)

  • Hair

Evidence Check · Castor oil

Castor oil for brows and lashes: does it thicken anything?

The castor-oil-for-lashes story is mostly anecdote and small preclinical work; systematic reviews find no strong human evidence for hair growth, while product formulations sometimes hide stronger, drug-like ingredients that do have effects and safety concerns.

  • Hair

Myth Busting · Castor oil

Castor oil and acne: why oil-cleansing advice goes wrong

Castor-heavy oil cleansing can remove makeup and even affect drug penetration, but the notion that castor oil ‘‘draws out’’ toxins or reliably clears acne is not supported by the research cited here. Evidence for helpful effects is patchy and mostly lab or formulation-level.

  • Skin

Evidence Check · Castor oil

Castor oil on your face: cleanser, moisturizer or myth?

Most evidence for castor oil’s effects comes from laboratory work, formulation studies, ocular or oral/denture trials, and material science—not from controlled tests on facial skin. That makes its actions plausible but not precisely mapped to regular face use.

  • Skin

Evidence Check · Castor oil

Castor oil and your hairline: what the evidence actually says

Lab models and computer docking raise plausible mechanisms for ricinoleic acid, and some animal work and reviews note cosmetic benefits; but well-designed human trials showing topical castor oil reliably produces new scalp hair are not available in the cited literature.

  • Hair

Reviewed

Sources

  1. Re-Review Summary of Ricinus Communis (Castor) Seed Oil and Ricinoleates as Used in Cosmetics. — Fiume MM, Bergfeld WF, Belsito DV, Cohen DE, Klaassen CD, Rettie AE, Ross D, Snyder PW, Tilton SC, Heldreth B. · International journal of toxicology · 2025
  2. Use of Castor Oil in Dermatology: A Narrative Review. — Girdler K, Cabatu A, Olds H, Potts GA. · Cureus · 2026
  3. An Exploratory Preclinical In Vivo Pilot Study Evaluating the Hair Growth-Promoting Effects of Rosmarinus officinalis and Ricinus communis Combination. — Mathenge A, Odongo E, Mauti R, Osee F. · BioMed research international · 2026
  4. Rosmagain™ as a Natural Therapeutic for Hair Regrowth and Scalp Health: A Double-Blind, Randomized, Three-Armed, Placebo-Controlled Clinical Trial. — Patel MN, Tuli N, Patel N, Merja A. · Cureus · 2025
  5. Preparation, characterization and in-vivo evaluation of nanoemulsion based hydrogel of ferulic acid in imiquimod-induced psoriasis in rats. — Naseer N, Kamran SH, Sultana M, Ishtiaq S, Siddique F, Sohail MF, Mastoi MI. · Scientific reports · 2026
  6. Lipid-based nanocarriers as versatile platforms for curcumin delivery in photodynamic therapy of skin cancer. — Viana AC, Holanda VM, Mazza MR, de Fátima Sousa Oliveira G, de Abreu Fantini MC, Pinto de Oliveira CL, Silva de Sousa EH, Araújo TG, Eloy JO, Petrilli R. · International journal of pharmaceutics · 2026
  7. Cryo-emulsion gel patches as versatile platform for dual drug delivery to wounds. — Wiedemann Y, Abdel-Mottaleb MMA, Lunter DJ. · International journal of pharmaceutics · 2026
  8. A Comprehensive Review of Plant-Based Cosmetic Oils (Virgin Coconut Oil, Olive Oil, Argan Oil, and Jojoba Oil): Chemical and Biological Properties and Their Cosmeceutical Applications. — Abdalla S, Aroua MK, Gew LT. · ACS omega · 2024
  9. Domesticated Argania spinosa in Eastern Morocco: HPLC-DAD/GC-MS Chemical Profiling, Antioxidant and Antidiabetic Activities, and Network Pharmacology-Guided Molecular Docking. — Azizi SE, Daoudi NE, Roubi M, Alami Merrouni I, Hendrawan AF, Bnouham M, Berrichi A, Dalli M, Legssyer B, Gseyra N. · International journal of molecular sciences · 2026
  10. Comparative Study of the Physicochemical Properties and Nutritional Quality of Argan Oil from Endemic and Planted Argania spinosa (L.) Fruit Trees in South-West Algeria. — Ould Safi M, Di Bella G, Nava V, Albergamo A, Bencheikh A, Boudeffeur S, Boughalia M, Kechairi R, Potortì AG. · Foods (Basel, Switzerland) · 2026
  11. Argan Oil: A Natural Bioactive Lipid Modulating Oxidative Stress and Inflammation. — Rabbaa S, Bouchab H, Laaziouez Y, Limami Y, Nasser B, Andreoletti P, Cherkaoui-Malki M, El Kebbaj R. · Antioxidants (Basel, Switzerland) · 2025
  12. Exploring the Impact of Extraction Methods on the Nutritional and Sensory Profiles of Argan Oil from Mostaganem Kernels. — Aridj T, Boukezzoula N, Tefiani C, Benabdelmoumene D, Chaalel A, Berrahal N, Tahlaiti A, Bentounes A, Różański H, Szumny A. · Foods (Basel, Switzerland) · 2026
  13. Effects of physical refining process on quality and stability of argan oil (Argania Spinosa (L.) Skeels). — Asbbane A, Bousaid Z, Guillaume D, El Harkaoui S, Matthäus B, Charrouf Z, Goh KW, Srasom N, Bouayahya A, Gharby S. · Scientific reports · 2024
  14. Development and characterization of dibenzalacetone-loaded oleogels as a potential photoprotective agents for sunscreen formulations. — Sheta NM, Taher AT, Rashwan KO, Mahmoud AM, Abuelella KE. · Scientific reports · 2026
  15. Green enrichment of argan oil (Argania spinosa L.) with thyme (Thymus vulgaris L.) and oregano (Origanum vulgare L.) leaves: Evaluating quality and stability improvements. — Oubannin S, Asbbane A, Goh KW, Singh J, Zafar I, Bouyahya A, Gharby S. · Food chemistry: X · 2024
  16. Ultrasound-assisted enrichment of argan oil (Argania spinosa L.) with thyme (Thymus vulgaris L), oregano (Origanum vulgare L.) and saffron (Crocus sativus L.) powders: Impact on bioactive compounds and oxidative stability. — Oubannin S, Asbbane A, Hallouch O, Nouj N, Goh KW, Bouyahya A, Gharby S. · Ultrasonics sonochemistry · 2025