Question explored with the scientific record
Castor oil for skin
The short version: the evidence retrieved does not test castor oil on human skin for barrier function, moisturization, or wound healing.
The retrieved studies are about industrial chemistry and microbiology. One study measured ricinoleic acid solubility in oils for a ketoconazole microemulsion [2]. Another showed ricinoleic acid inhibits the intestinal Na+-H+ exchanger in rabbit cells [10]. A third found ricinoleic acid stimulates eicosanoid production in rat and human colon tissue [15]. None of these test topical application on human skin.
The antifungal data is the closest match. Ricinoleic acid had a minimum inhibitory concentration of 2.4 g/L against Aspergillus niger [17]. That is a lab dish result, not a clinical trial on dermatitis or wound healing. The castor oil study in mice was about oral prophylaxis against parasitic worm penetration, not skin [16].
The evidence does not contain a single human trial of castor oil on skin for any outcome you asked about. The gap itself matters. There is no basis here to say it works or does not work for your skin.
My call: the evidence retrieved does not address the question. Confidence: not clear.
Sources examined 17
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Attainment of hydrogel-thickened nanoemulsions with tea tree oil (Melaleuca alternifolia) and retinyl palmitate
Hydrogel-thickened nanoemulsions combining tea tree oil and retinyl palmitate were prepared by phase inversion, using several polymers to increase viscosity while maintaining ~90 nm droplets and pseudoplastic rheology for potential topical delivery.
DOI: 10.5897/ajb11.249 -
Improvement of the microbiological activity of topical ketoconazole using microemulsion systems
The study designs and evaluates topical ketoconazole microemulsions using Labrafil M2125 or IPM oils with Tween 80/isopropanol as surfactant/cosurfactant to enhance antifungal activity against Candida albicans, finding IPM-based formulations to be more stable and more effective …
DOI: 10.1016/s1773-2247(12)50083-3 -
Synthesis of Ricinoleic Acid Estolides by the Esterification of Ricinoleic Acids Using Functional Acid Ionic Liquids as Catalysts
This study investigates the synthesis of ricinoleic acid estolides through the esterification of ricinoleic acids using functional acid ionic liquids as catalysts, optimizing reaction conditions to achieve high yields in a solvent-free system.
DOI: 10.5650/jos.ess17031 -
Free Saturated Oxo Fatty Acids (SOFAs) and Ricinoleic Acid in Milk Determined by a Liquid Chromatography-High-Resolution Mass Spectrometry (LC-HRMS) Method
A rapid LC-HRMS method with mild sample preparation was developed and validated to detect and quantify a family of saturated oxo fatty acids (SOFAs) and ricinoleic acid in cow and goat milk, revealing abundant oxo-regioisomers and unexpectedly high ricinoleic acid levels likely …
DOI: 10.3390/metabo11010046 -
Production of conjugated linoleic acids through KOH-catalyzed dehydration of ricinoleic acid
This study demonstrates that potassium hydroxide (KOH) can effectively replace the expensive dehydrating reagent DBU in the production of conjugated linoleic acids (CLA) from ricinoleic acid, achieving a conversion efficiency of 77% at 80°C.
DOI: 10.1016/s0009-3084(02)00052-x -
Production of ω-hydroxyundec-9-enoic acid and n-heptanoic acid from ricinoleic acid by recombinant Escherichia coli-based biocatalyst
This study engineered a recombinant Escherichia coli-based biocatalytic process to efficiently produce -hydroxyundec-9-enoic acid and n-heptanoic acid from ricinoleic acid, achieving a final product concentration of 20 mM and a productivity rate of 3.2 mM/h.
DOI: 10.1016/j.procbio.2014.01.025 -
Yarrowia lipolytica as a biotechnological chassis to produce usual and unusual fatty acids
A 2015 review that surveys Yarrowia lipolytica as a biotechnological chassis for producing both usual lipids and unusual fatty acids, detailing lipid metabolism, metabolic engineering tools, case studies of CLA, ricinoleic acid, EPA/DHA, and prospects for synthetic biology and o…
DOI: 10.1016/j.plipres.2015.12.001 -
Isolation and characterisation of 8-hydroxy-3 Z ,5 Z -tetradecadienoic acid, a putative intermediate in Pichia guilliermondii γ-decalactone biosynthesis from ricinoleic acid
This study reports the isolation and characterization of 8-hydroxy-3Z,5Z-tetradecadienoic acid, a putative intermediate in the biosynthesis of Q-decalactone from ricinoleic acid by the yeast Pichia guilliermondii, using various analytical techniques.
DOI: 10.1111/j.1574-6968.2002.tb11109.x -
A simple, scalable protocol for the synthesis of ricinoleic acid-functionalised superparamagnetic nanoparticles with tunable size, shape, and hydrophobic or hydrophilic properties
A scalable, one-pot synthesis uses ricinoleic acid as both precursor and capping agent to produce tunable superparamagnetic iron oxide nanoparticles and ferrites with controllable size/shape and switchable hydrophobic or hydrophilic surface properties.
DOI: 10.1039/d5na00150a -
Fatty acid-induced alterations in transport systems of the small intestinal brush-border membrane
Free fatty acids inhibit multiple intestinal brush-border transport systems in rabbit BBMV, most notably the Na+-H+ exchanger, with unsaturated acids like oleic and ricinoleic acids showing potent, partially reversible, non-competitive inhibition that may arise from direct trans…
DOI: 10.1016/0006-2952(88)90800-3 -
Synthesis and Physical Properties of Estolide Ester Using Saturated Fatty Acid and Ricinoleic Acid
This study investigates the synthesis of estolide esters from ricinoleic acid and various saturated fatty acids, revealing their superior low-temperature properties and high flash points, making them suitable for applications in cold environments.
DOI: 10.1155/2011/263624 -
Genetic Engineering of Lesquerella with Increased Ricinoleic Acid Content in Seed Oil
Genetic engineering of Lesquerella fendleri seeds by RNAi silencing of desaturation and elongation genes led to substantial increases in 18:1OH (ricinoleic acid) and altered fatty acid flux, revealing both the potential and the bottlenecks for producing castor-like hydroxy fatty…
DOI: 10.3390/plants10061093 -
Unusual fatty acids of Cordia rothii seed oil
This study investigates the unusual fatty acid composition of Cordia rothii seed oil, identifying significant amounts of ricinoleic, malvalic, and sterculic acids among others.
DOI: 10.1002/jsfa.2740580219 -
Functional Ionic Liquids Catalyzed the Esterification of Ricinoleic Acid with Methanol to Prepare Biodiesel: Optimization by Response Surface Methodology
This study investigates the use of functional ionic liquids as catalysts for the esterification of ricinoleic acid with methanol to produce biodiesel, optimizing the process through response surface methodology to achieve a degree of esterification of 92.3 ± 1.7%.
DOI: 10.1007/s11746-016-2826-5 -
Eicosanoid formation by mammalian intestine. Effects of some intestinal secretagogues
This study investigates how mammalian intestinal tissues from multiple species metabolize arachidonic acid into cyclo-oxygenase and lipoxygenase products in vitro, showing that several intestinal secretagogues robustly stimulate eicosanoid formation (especially ricinoleic acid a…
DOI: 10.1016/0014-2999(87)90344-X -
Schistosoma mansoni: Experimental chemoprophylaxis in mice using oral anti-penetration agents
This study evaluated oral anti-penetration agents and praziquantel as chemoprophylactics against Schistosoma mansoni in mice, finding castor oil and ricinoleic acid highly protective against cercarial penetration, Cremophor El having its own protective effect, and praziquantel’s…
DOI: 10.1016/0014-4894(89)90072-6 -
Antifungal Hydroxy Fatty Acids Produced during Sourdough Fermentation: Microbial and Enzymatic Pathways, and Antifungal Activity in Bread
Monohydroxy C18:1 fatty acids produced from linoleic acid by Lactobacillus hammesii in sourdough exhibit antifungal activity, and coriolic acid enhances this effect, delaying mold growth in bread and suggesting a natural sourdough-based preservation mechanism.
DOI: 10.1128/aem.03784-12