pediaCastor oil, obtained from the seeds of Ricinus communis L. (Euphorbiaceae family) by cold-press method, is a viscous, clear-yellowish vegetable oil. With risinoleic acid content of 85–92% — the richest natural source of risinoleic acid — castor oil holds a unique position in soap-making for producing transparent soaps, foam stability, and moisturization. Used in 24 Chailea products, castor oil is the most common auxiliary oil in all product formulations.
This article is not a product promotion. The information presented does not contain any therapeutic claims.
Botanical source
Ricinus communis L. (castor plant / palma Christi), native to Africa, is a fast-growing plant. Its seeds contain the highly toxic ricin protein — but ricin does not enter cold-pressed oil (protein is not soluble in oil). India produces 80% of world castor oil production.
Chemical profile
Risinoleic acid: 85–92%
The most distinctive feature of castor oil is its content of 85–92% risinoleic acid (12-hydroxy-9-cis-octadecenoic acid, C18:1-OH). Risinoleic acid, bearing a hydroxyl (-OH) group, is a rare fatty acid — this hydroxyl group gives castor oil extraordinary viscosity, water-attracting (humectant) capacity, and compatibility with other oils. Castor oil is the only commercial vegetable oil with 80%+ risinoleic acid in nature.
Place in scientific literature
Emollient and skin barrier
The hydroxyl group of risinoleic acid creates an occlusive film on the skin surface, reducing transepidermal water loss (TEWL). In a 2018 review published in Journal of the American Oil Chemists' Society by Vieira et al., cosmetic and pharmacological properties of castor oil were comprehensively evaluated.
Laxative effect (oral — unrelated to cosmetics)
The most well-known pharmacological property of castor oil is its potent laxative effect when taken orally. This effect occurs through risinoleic acid activating intestinal EP3 prostanoid receptors. This property is unrelated to cosmetic use.
Safety profile
The CIR panel assessed Ricinus Communis Seed Oil as safe for cosmetic use. Safe for topical use. Ricin toxin does not enter cold-pressed oil. Rare contact dermatitis reports exist.
Castor oil in soap-making
Foam booster and transparency
Castor oil serves two critical functions in soap-making: foam stability (sodium ricinoleate soap stabilizes the foam structure of soap and provides longer-lasting foam) and transparency (castor oil is a key ingredient in producing transparent/clear soaps — the hydroxyl group of risinoleic acid imparts transparency to the soap structure). SAP value (NaOH) approximately 0.128. Usage rate: 5–10% (higher rates may make soap soft and sticky).
Castor oil types and quality
Cold-pressed castor oil
Cosmetic and soap-making grade. Clear-yellowish color, light odor. USP/BP grade available. The preferred form in soap-making.
Jamaican black castor oil (JBCO)
A dark brown-black, intensely aromatic variety of castor oil obtained by roasting the seeds. Contains terrestrial ash particles. Popular in hair care — especially for curly and Afro-textured hair. Can be used in soap-making but its dark color and strong odor define the soap's character.
Industrial castor oil
Castor oil is industrially used in bioplastic production (polyamide 11 — Rilsan), paints and varnishes, lubricating oils, biodiesel, and pharmaceuticals (laxative preparations). The hydroxyl group of risinoleic acid, with its structure suited to chemical modification, makes it a valuable starting material for polymer chemistry.
Unique role of castor oil in soap-making
Castor oil holds a unique role in soap-making that no other oil can fully replace. Sodium ricinoleate (the soap salt of castor oil), unlike other soap salts, has the capacity to attract both water and oils — by virtue of its amphiphilic structure, it enhances foam stability. Additionally, sodium ricinoleate imparts slight transparency to soap. In transparent/clear glycerin soaps, castor oil at 5–10% is an indispensable ingredient. Used at 5–10% in soap — higher rates may make soap soft and sticky.
Frequently asked questions
What does castor oil do in soap?
It provides foam stability and is a key ingredient in producing transparent soap. Used at 5–10%.
Is there a ricin risk in castor oil?
No — ricin is a protein and does not enter cold-pressed oil. Cosmetic-grade castor oil contains no ricin.
Castor oil plant and toxicity note
Ricin: one of the world's most toxic proteins
Ricinus communis seeds contain ricin, an extremely toxic protein — a few milligrams can be lethal. Ricin, due to its biological weapons potential, is monitored under the "Biological Weapons Convention" and "Chemical Weapons Convention." However, this toxicity does not concern cosmetic castor oil users: ricin has a protein structure and is not soluble in oil, does not enter oil during the cold-press process, cosmetic-grade castor oil contains no ricin, and topical application is entirely distinct from ingestion exposure.
History of the castor oil plant
The castor oil plant has been known since Ancient Egypt — recorded in the Ebers Papyrus (1550 BCE) as an eye drop and hair care product. The epithet "Palma Christi" (Palm of Christ), used in medieval Europe, reflects the plant's revered healing potential in that era. India produces 80% of world castor oil production — the state of Gujarat is the primary production center.
Castor oil in hair care
Castor oil is one of the most widely used vegetable oils in hair care contexts. The humectant properties of risinoleic acid carry potential for moisture-binding to hair. The claim that it accelerates hair growth is widespread but lacks strong clinical evidence supporting it. Castor oil's high viscosity coats the hair strand and may provide protection against mechanical damage.
Castor oil and modern industry
Castor oil holds increasingly growing importance in modern industry, where alternatives to petrochemicals are being researched. The hydroxyl group of risinoleic acid offers a structure highly suited to chemical modification, enabling its use in bioplastic production (Rilsan PA11 — Arkema's polyamide 11 product), paint and varnish industries (alkyd resins), lubricating oils (high viscosity and thermal stability), and pharmaceutical industry (laxative preparations, pharmaceutical coating materials). Annual world castor oil production is approximately 1.5–2 million tons, with India producing 80% of output.
Castor oil and bioeconomy
The castor oil plant is resistant to arid and semi-arid climate conditions and can grow on marginal lands — this property is valuable from bioeconomy and sustainable agriculture perspectives. As an oil plant that does not compete with food crops, its potential as a feedstock for biofuel and bioplastic is being researched.
Chailea products containing this ingredient
Castor oil (Ricinus Communis Seed Oil) is used in 24 Chailea products as a foam stabilizer and transparency provider. View all products →
References
1. Vieira, C., et al. (2018). An overview on Ricinus communis (castor oil). Journal of the American Oil Chemists' Society. doi:10.1002/aocs.12119
2. CIR Expert Panel. Safety Assessment of Ricinus Communis-derived ingredients.