Chapter 11: The supporting cast · Part 2: Thickeners
Hydrogenated castor oil
No badge
The worst fact: it comes from the castor bean, whose ricin is a "highly toxic protein": the estimated lethal oral dose is 1 to 20 mg per kg of body weight, and poisonings have followed eating anywhere from a single seed to 30.
Why brands use it: it forms fine, thread-like crystals that hold a laundry liquid together so it doesn't separate, typically at under 1% (about 0.1 to 0.8%).
Take care if: no specific group. Castor bean dust (not the oil) has caused allergies in workers handling the beans and sacks contaminated with them.
Comes from: castor oil, pressed from the seed of Ricinus communis, then hardened with hydrogen over a nickel catalyst. (A catalyst isn't an ingredient, so no 🛢 badge.)
Myth check: "It contains ricin": no. "Castor oil does not contain ricin because ricin does not partition into the oil."
Contaminants: nil.
Fair to say: a US cosmetic review found castor oil and hydrogenated castor oil safe as used, and castor oil "is not a significant skin irritant, sensitizer, or photosensitizer".
Correct as of November 2026. What the badges mean
Sources
- Cosmetic Ingredient Review: castor oil and hydrogenated castor oil (2007); styrene/acrylates copolymers (2014); glycol stearate (2023); microbial gums; galactomannans; PEGs (2005).
- GreenScreen assessment: hydrogenated castor oil.
- Worbs S et al. Ricinus communis intoxications in human and veterinary medicine. Toxins 2011.
The full source list is at the end of Chapter 11.