What it does
- Conditions and adds shine to hair, brows and lashes.
- Occlusive — softens and helps seal in moisture on skin and lips.
- Gives slip and a glossy finish.
How it works
Castor oil is unusually rich in ricinoleic acid, giving it a thick, glossy, occlusive character widely documented for conditioning and shine. It is popular in brow, lash and hair products; however, robust evidence that it makes hair grow is limited, so it is best positioned as a conditioning, shine-enhancing oil rather than a proven growth active.
Use level
- Typical use level
- typically 1–10% (or higher in balms)
Commonly used at 1–10% (higher in brow/lip balms). Its high viscosity usually means blending with lighter oils.
Formulation considerations
- Oil-soluble and very viscous; blend with lighter oils for spreadability.
- Glossy, heavy finish.
- Stable relative to polyunsaturated oils.
What it pairs with & what to avoid
Pairs well with
- Lighter oils (to thin the texture)
- Conditioning agents
Use with care / avoid
- Overstating hair-growth claims (evidence is limited)
Regulatory status
Castor (Ricinus communis) seed oil is listed in the EU CosIng database and is a long-established emollient.
Common questions
Does castor oil grow hair or brows?
Evidence that it grows hair is limited; it is best understood as a conditioning, shine-enhancing oil rather than a proven growth active.
Why is castor oil so thick?
It is rich in ricinoleic acid, which gives a viscous, glossy texture.
What percentage of castor oil is used?
Commonly 1–10%, higher in brow and lip balms.