Castor Oil: Shine and Softness Instead of a Growth Miracle
Active Ingredients Glossary · R
INCI: Ricinus Communis Seed Oil
Castor oil is the most viscous of all common vegetable oils. That’s exactly what makes it appealing for lip gloss, lip care, and hair oils: it provides shine, hold, and a smooth feel. However, there are also persistent claims circulating about the oil that don’t hold up to scrutiny.
What is castor oil?
Castor oil is pressed from the seeds of the castor bean plant. It consists largely of ricinoleic acid, a fatty acid with an additional hydroxyl group. This makes the oil unusually viscous and comparatively polar, which is why it wets color pigments well and provides shine and even color in lipsticks and glosses.
The seeds themselves contain the toxic protein ricin. It remains in the residue during pressing and is destroyed during processing; cosmetic castor oil does not contain it. For skincare, cold-pressed, purified oil is usually used, which is light in color and nearly odorless. Dark, roasted oil is a specialty and is not necessary for the product’s effectiveness.
Effects: What’s Been Proven
Two out of five bars: Castor oil has a moisturizing effect, leaves a glossy film on the skin, lips, and hair, and makes the strands more supple. This is easy to understand, but as a skincare oil, it has hardly been studied in clinical trials. There are no reliable human studies supporting the popular claims that it promotes the growth of hair, eyelashes, or eyebrows. To be honest: a useful texturizer and shine enhancer, not a growth stimulant.
Application & Combination
On its own, castor oil is very sticky and difficult to wash out. In hair oils, it is therefore blended with lighter oils that make it easier to apply. Work it into the lengths and ends as a pre-wash, let it sit, and then wash it out thoroughly with shampoo. In lip products, it provides shine and a nourished feel; in hydrogel patches, it serves as a nourishing oil component.
Pairs well with
✓ Almond, grapeseed, and jojoba oils—lighter oils make castor oil easier to apply
✓ Beeswax and plant butters – in lip care for hold and protection
✓ Sugar—in lip scrubs, the sugar exfoliates while the oil nourishes
Note
! Very thick when undiluted: use only small amounts in hair and rinse thoroughly
! Contact allergies are rare but possible—test new products on a small area first
! Avoid contact with the eyes, even when applying to the eyelashes
Castor oil in the BONSANA lineup
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Go to HAIR SYRUP →Frequently Asked Questions About Castor Oil
Does castor oil make eyelashes grow longer?
There is no reliable evidence to support this. Castor oil can nourish eyelashes and make them appear shinier, but based on current knowledge, it does not affect their length or number.
Is castor oil toxic?
No, cosmetic castor oil is safe. The toxic substance ricin is found in the seeds; it remains in the residue during pressing and is destroyed during processing. It is not present in the oil.
How do I wash castor oil out of my hair?
It’s best to apply shampoo to dry, oiled hair, massage it in, and only then add water. If there’s a lot of oil, a second wash helps. Blends with lighter oils are much easier to wash out.
Why is castor oil in lip gloss?
Its viscous texture provides shine and hold, and it distributes color pigments evenly. At the same time, it leaves the lips feeling nourished.
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