The oil derived from the seed of the Ricinus communis plant and its primary constituent,
Ricinoleic Acid, along with certain of its
salts and
esters function primarily as skin-conditioning agents,
emulsion stabilizers, and
surfactants in
cosmetics, although other functions are described. Ricinus Communis (Castor) Seed Oil is the naming convention for
castor oil used in
cosmetics. It is produced by cold pressing the seeds and subsequent clarification of the oil by heat.
Castor oil does not contain
ricin because
ricin does not partition into the oil.
Castor oil and Glyceryl Ricinoleate absorb ultraviolet (UV) light, with a maximum absorbance at 270 nm.
Castor oil and Hydrogenated
Castor Oil reportedly were used in 769 and 202 cosmetic products, respectively, in 2002; fewer uses were reported for the other ingredients in this group. The highest reported use concentration (81%) for
castor oil is associated with lipstick.
Castor oil is classified by Food and Drug Administration (FDA) as generally recognized as safe and effective for use as a stimulant
laxative. The Joint Food and Agriculture Organization (FAO)/World Health Organization (WHO) Expert Committee on
Food Additives established an acceptable daily
castor oil intake (for man) of 0 to 0.7 mg/kg
body weight.
Castor oil is hydrolyzed in the small intestine by pancreatic
enzymes, leading to the release of
glycerol and
Ricinoleic Acid, although 3,6-epoxyoctanedioic
acid, 3,6-epoxydecanedioic
acid, and 3,6-epoxydodecanedioic
acid also appear to be metabolites.
Castor oil and
Ricinoleic Acid can enhance the transdermal penetration of other chemicals. Although chemically similar to
prostaglandin E(1),
Ricinoleic Acid did not have the same physiological properties. These ingredients are not acute toxicants, and a National Toxicology Program (NTP) subchronic oral toxicity study using
castor oil at concentrations up to 10% in the diet of rats was not toxic. Other subchronic studies of
castor oil produced similar findings. Undiluted
castor oil produced minimal
ocular toxicity in one study, but none in another. Undiluted
castor oil was severely irritating to rabbit skin in one study, only slightly irritating in another, mildly irritating to guinea pig and rat skin, but not irritating to miniature swine skin.
Ricinoleic Acid was nonirritating in mice and in one rabbit study, but produced well-defined
erythema at abraded and intact skin sites in another rabbit study.
Zinc Ricinoleate was not a sensitizer in guinea pigs. Neither
castor oil nor
Sodium Ricinoleate was genotoxic in bacterial or mammalian test systems.
Ricinoleic Acid produced no
neoplasms or
hyperplasia in one mouse study and was not a
tumor promoter in another mouse study, but did produce epidermal
hyperplasia.
Castor oil extract had a strong suppressive effect on S(180) body
tumors and ARS
ascites cancer in male Kunming mice. No dose-related reproductive toxicity was found in mice fed up to 10%
castor oil for 13 weeks. Female rats injected intramuscularly with
castor oil on the first day after estrus had suppressed ovarian folliculogenesis and anti-implantation and abortive effects.
Castor oil used as a vehicle control in rats receiving
subcutaneous injections had no effect on spermatogenesis. A
methanol extract of Ricinus communis var. minor seeds (
ether-soluble fraction) produced anti-implantation, anticonceptive, and estrogenic activity in rats and mice. Clinically,
castor oil has been used to stimulate labor.
Castor oil is not a significant skin
irritant, sensitizer, or
photosensitizer in human clinical tests, but patients with occupational
dermatoses may have a positive reaction to
castor oil or
Ricinoleic Acid. The instillation of a
castor oil solution into the eyes of nine patients resulted in mild and transient discomfort and minor epithelial changes. In another study involving 100 patients, the instillation of
castor oil produced corneal epithelial cell death and continuity breaks in the epithelium. Because
castor oil contains
Ricinoleic Acid as the primary
fatty acid group, the Cosmetic Ingredient Review (CIR) Expert Panel considered the safety test data on the oil broadly applicable to this entire group of cosmetic ingredients. The available data demonstrate few toxic effects. Although animal studies indicate no significant
irritant or sensitization potential, positive reactions to
Ricinoleic Acid in selected populations with identified
dermatoses did suggest that sensitization reactions may be higher in that population. Overall, however, the clinical experience suggests that sensitization reactions are seen infrequently. In the absence of inhalation toxicity data on these ingredients, the Panel determined that these ingredients can be used safely in aerosolized cosmetic products because the particle sizes produced are not respirable. Overall, the CIR Expert Panel concluded that these cosmetic ingredients are safe in the practices of use and concentrations as described in this safety assessment.