Castor Oil in Our Under Eye Roller and Beard Oil

We use castor oil in two formulas: The Royal Kalahari Under Eye and Lip Serum Roller Oil and GRR Oil Beard Oil. In both, it is one oil in a blend rather than the whole formula. Castor oil is roughly 90 percent ricinoleic acid, a rare fatty acid that makes it thick, glossy and good at clinging to skin and hair. That gives each blend cushion and staying power, while the lighter oils around it keep it from feeling sticky.

The oil laboratories use as a ruler

Castor oil is pressed from the seeds of Ricinus communis. It is up to 90 percent ricinoleic acid, with about 4 percent linoleic, 3 percent oleic, 1 percent stearic and less than 1 percent linolenic acid. Ricinoleic acid is an 18-carbon fatty acid with a hydroxyl group partway along its chain, and castor oil is essentially the only commercial source of it. In one analysis, molecules made of three ricinoleic acids on a single glycerol backbone accounted for 84.1 percent of the oil.

That uniformity has a practical side. Because castor oil's composition is so constant, laboratories have long used it as a standard for measuring viscosity. When something needs to be calibrated for thickness, castor oil is the ruler.

And it is thick. On one common scale its viscosity sits around 293, against roughly 47 for olive oil. Rub a drop between your fingers and you feel the difference: castor oil behaves less like a serum and more like a protective layer.

What castor oil adds to a blend

A film that holds moisture in

Castor oil's thickness lets it form a thin film on the skin that reduces transepidermal water loss, the water that evaporates through skin into the air. Applied over damp or already-moisturized skin, it helps keep that water where it is. In a blend, even a share of castor oil gives the whole formula more staying power.

Gloss and cushion

It has a slightly tacky, glossy finish. On lips that reads as a soft shine, and under the eyes as a cushioned, comfortable feel.

Stability

Castor oil resists going stale better than most plant oils. In one study, its resistance to oxidation was higher than that of argan, nigella, olive and sesame oils, holding out for 35.5 hours at 110 degrees Celsius before breaking down. Anyone who has opened a face oil after a few months and caught a faint crayon smell will appreciate an oil that does not turn quickly.

Castor oil in the Under Eye and Lip Serum Roller Oil

Two places on the face have almost no oil glands of their own: the skin under the eye and the lips. They cannot seal themselves, so they dry out first. Castor oil's film suits them better than almost any other oil, but on its own it is too thick and sticky to spread evenly over such delicate skin. So we blend it.

The roller is built from the same family of oils as The Royal Kalahari Face Serum: Kalahari melon, baobab, mongongo, passion fruit, camellia, grapeseed and tamanu. Castor oil joins them for a soft, glossy cushion, and monoi de Tahiti adds a faint floral warmth. Vitamin E keeps the oils fresh, and a vitamin C complex adds brightness. The steel roller ball meters the dose and spreads it in a thin, even line without dragging, so the film goes on light enough to wear under concealer.

Trace a line under each eye and over your lips, morning and night. Under the eyes, skin looks brighter, smoother and softly hydrated; on lips it leaves a soft, nourished gloss. It suits normal, dry, mature and sensitive skin, and its amber glass bottle with a gold cap slips into any bag.

Castor oil in GRR Oil Beard Oil

GRR Oil is a conditioning beard oil for a softer, smoother-looking beard without greasy shine. Its base is a blend of jojoba, Kalahari melon seed, avocado, coconut and castor oils with squalene, which spread easily through the hair and sink in fast. Castor oil adds its soft, glossy cushion to that base, and the formula is meant for both the beard and the skin beneath it.

Warm a few drops between your palms and work them through the beard after you wash. The 1 oz bottle has a dropper, so you pour exactly what you need. The beard feels softer and easier to comb, and the scent, from our own perfumery, is subtle and refined. Like the roller, it is made by hand in small batches in Brooklyn.

What castor oil does not do

Being honest about an ingredient is part of using it well. Castor oil can make fine lines look softer by keeping the skin around them moisturized, as any good moisturizer does, but the effect is on the surface. Nothing in its chemistry tells skin to make new collagen, and it does not tighten skin permanently.

On under-eye darkness, a small exploratory trial published in the Journal of Cosmetic Dermatology in 2024 looked at a castor oil cream used under the eyes. A single-arm trial with no comparison group is early evidence, not proof, and we do not make that claim for the roller.

Castor oil is also a known, if uncommon, cause of skin reactions, most often reported with lip products. Patch test on the inner arm before using any new castor oil product. You can read more about castor oil, and every other ingredient we use, in our Ingredient Library.

Questions about castor oil in our formulas

Which Marianella products contain castor oil?

The Royal Kalahari Under Eye and Lip Serum Roller Oil and GRR Oil Beard Oil, along with sets that include the roller, such as The Kalahari Icon Duo and The Youth Authority Face Set.

Is GRR Oil only for the beard?

It is made for both the beard and the skin beneath it. A few drops soften the hair and leave the skin underneath feeling moisturized.

Will the roller lighten dark circles?

We do not claim that. The roller leaves under-eye skin looking brighter, smoother and softly hydrated, and the research on castor oil and under-eye darkness is still early.

Can castor oil cause a reaction?

Rarely, but it can, most often in lip products. Try a new castor oil product on a small patch of skin first.