Castor Oil: Natural Sun Protection Research

Last updated August 3, 2026

Castor oil is extracted from the seeds of Ricinus communis, a plant native to tropical Africa and Asia. Scientific research indicates an SPF value of 5.687, placing it in the middle range of natural oils for UV absorption, though still insufficient for adequate sun protection.

Recommended: Sky Organics Cold Pressed Organic Castor Oil — for hair and skincare — not a sunscreen

Origin and Production

Castor oil comes from the seeds of Ricinus communis, commonly known as the castor bean plant. Despite its name, it's not a true bean but a member of the spurge family (Euphorbiaceae). The plant is now cultivated worldwide, with India producing nearly 90% of global supply, followed by China and Brazil. The oil is extracted through cold pressing or solvent extraction of the seeds, which contain 40-60% oil by weight. The seeds contain ricin, a highly toxic protein, but the oil is safe as ricin is water-soluble and doesn't transfer to the oil during processing. Castor oil is unique among vegetable oils due to its high ricinoleic acid content (85-95%), which gives it distinctive properties.

Scientific Research on UV Protection

Kaur & Saraf Study (2010)

The SPF value of 5.687 for castor oil was established in Kaur & Saraf's comprehensive study published in Pharmacognosy Research. Using UV spectrophotometric methods to measure absorption in the UVB range (290-320 nm), castor oil showed moderate photoprotective activity among the natural oils tested. As a fixed oil rather than an essential oil, it demonstrates greater stability under UV exposure.

Reference: Kaur CD, Saraf S. In vitro sun protection factor determination of herbal oils used in cosmetics. Pharmacognosy Research. 2010;2(1):22-25.

Fixed Oil Stability Advantages

Unlike volatile essential oils, castor oil is a fixed oil with better photostability. Its thick, viscous nature (due to ricinoleic acid) provides a protective film on the skin that may enhance its limited UV-blocking properties. However, the SPF of 5.687 remains far below the minimum SPF 15 recommended for daily protection and SPF 30 for extended sun exposure.

Additional Benefits

Beyond its limited UV absorption, castor oil is renowned for numerous cosmetic and therapeutic applications. Its high ricinoleic acid content provides anti-inflammatory and antimicrobial properties. The oil is widely used for hair growth promotion, particularly for eyebrows and eyelashes, though scientific evidence remains limited. Its humectant properties make it an effective moisturizer for dry skin. In traditional medicine, castor oil has been used as a laxative (though this use requires medical supervision). The oil's thick consistency makes it useful in lip balms and protective barriers for minor wounds. However, some individuals may experience allergic reactions, so patch testing is recommended before widespread use.

Products Tested in Scientific Research

The following castor oil products and formulations have been tested in peer-reviewed SPF studies:

Pure Oil SPF Testing

Regional Origin Studies

Processing Method Comparisons

Commercial Brand Analysis

Formulation Enhancement Studies

Specialty Applications

Hair and Scalp Studies

Comparison and Recommendations

Castor oil's SPF of 5.687 places it below coconut oil (7.119) and olive oil (7.549) but above many other natural oils like almond (4.659) and sesame (1.771). Its thick consistency makes it less pleasant for general skin application compared to lighter oils, though this same property makes it excellent for targeted applications like hair and eyebrow treatments.

For those interested in high-quality castor oil for cosmetic or therapeutic use, we recommend Sky Organics Cold Pressed Organic Castor Oil. While it offers minimal sun protection, castor oil should never replace proper sunscreen for UV protection.

Recommended: Sky Organics Cold Pressed Organic Castor Oil — for hair and skincare — not a sunscreen

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