All you need to know about castor oil.

Like all plant-based oils, the castor oil is composed of fatty acids, but it contains several vitamins and bioactive compounds that support its skincare benefits. The table below lists the molecules in castor oil and their cosmetic properties.

If castoroil is so popular for formulating skin creams and serums, it is due to the many benefits it provides:

• Castor oil hydrates the skin and strengthens the skin barrier.

  Castor oil is recognized for its hydrating properties, beneficial for the dry skin. These benefits stem from its high oleic acid content, a fatty acid present in sebum that reinforces the hydrolipidic film. Linoleic acid in castor oil inserts between corneocytes, the cells of the stratum corneum, which supports cell cohesion and limits water loss. These hydrating effects were confirmed by a clinical trial involving 15 participants with dry skin. After applying a castor oil-based formulation for ten days, an average increase of ten percent in skin hydration was measured by bioelectrical impedance.

• Castor oil could soothe skin and reduce irritation.

  Castor oil could soothe sensitive or redness-prone skin. Some studies suggest it may inhibit phospholipase A2, the enzyme that releases arachidonic acid, a pro-inflammatory precursor. By reducing the availability of this fatty acid, castor oil could limit prostaglandin and leukotriene formation, two key mediators in the inflammatory response. But studies to date on the anti-inflammatory properties of castor oil were conducted in rodents. Clinical studies are needed to confirm its soothing potential when applied topically.

• Castor oil helps protect skin from oxidative stress.

  Castor oil contains vitamin E, an antioxidant molecule known for its ability to neutralize free radicals. These unstable compounds, generated by UV exposure or pollution, degrade the skin’s structural proteins and promote the early appearance of wrinkles or pigmented spots. The antioxidant activity of castor oil was evaluated by a DPPH assay, with a median inhibitory concentration (IC50) measured at 19.02 µg/mL, compared to 2.36 µg/mL for ascorbic acid, used as a reference. This capacity to trap free radicals suggests that castor oil can help protect the skin from the harmful effects of oxidative stress and prevent photoaging.

• Castor oil appears to affect wrinkles..

  A study involving 22 participants with crow’s feet wrinkles suggests castor oil may also reduce wrinkles. For two months, volunteers applied a cream containing 10% castor oil around their eye area twice daily. At the end of the study, a mean improvement of 33% in wrinkle score was measured, while no side effects were reported.

• Castor oil may attenuate pigmented spots.

  Castor oil may also help reduce the appearance of brown spots. A clinical study of around twenty participants with pigmented dark circles found an average pigmentation improvement of 8.2% after 60 days of twice-daily application of a 10% castor oil treatment. The precise mechanism remains unclear. Castor oil is thought to inhibit tyrosinase, reducing melanin production that causes hyperpigmentation.

• Castor oil may prevent fungal infections.

  Finally, castor oil appears to have a potential antifungal activity to prevent fungal infections, whether on the skin or the nails. One study compared the effect of castor oil on the fungus Cunninghamella bertholletiae, responsible for certain fungal infections, to that of standard antifungal agents through disc diffusion and minimum inhibitory concentration (MIC) tests. The average inhibition zone for castor oil was 22.44 mm, compared with 20.66 mm for amphotericin B. The MIC was similar (1.72 µg/ml for castor oil versus 1.66 µg/ml for amphotericin B). This suggests castor oil could help prevent fungal infections.

The castor oil provides benefits for hair, lashes, brows, and beard hair. It may help stimulate their growth. Studies show that prostaglandin D2 (PGD2), a molecule that inhibits hair growth, is elevated in certain forms of alopecia. Ricinoleic acid from castor oil may reduce PGD2 expression, creating a favorable environment for growth. However, while a few clinical trials exist, more research is needed to confirm castor oil’s effect on hair and facial hair growth.

Beyond its potential effect, castor oil hydrates and nourishes hair fibers and follicles. Its high fatty acid content forms a protective film on their surface, reducing moisture loss. By inserting between cuticle lipids, the fatty acids help align the cuticle scales. This alignment improves light reflection and increases shine. Castor oil provides antioxidant and antifungal benefits that support the scalp or skin beneath the beard. Antioxidants neutralize free radicals linked to premature aging of the hair fiber and bulb, while antifungal activity supports skin flora balance.

The castor oil is viewed with caution due to ricin, a toxin naturally present in castor seeds. However, this concern is unfounded for topical use because ricin is a water-soluble protein that stays in the seed cake after extraction and does not enter the final oil. Castor oil produced by cold pressing or mechanical extraction undergoes a rigorous process that eliminates this toxin.

When applied topically, castor oil poses no known hazards and has a favorable safety profile.

It is suitable for sensitive skin and can be used by pregnant or breastfeeding people and young children. Its high viscosity is one of its few practical drawbacks but poses no risk. It can be uncomfortable for oily skin, whose high sebum production forms a protective hydrolipidic film that may not be relevant to weigh down with a rich oil like that of castor oil. Despite this, the castor oil has a low comedogenicity rating (1) and is not considered to promote comedone formation.