Does castor oil cause tanning?

Thecastor oil is a vegetable oil extracted from the seed of the shrub Ricinus Communis. Originally from tropical Africa, it is now cultivated all over the world. In order to obtain high-quality castor oil, the extraction is preferably done by the first cold pressing. Regarding its composition, castor oil is rich in fatty acids, particularly in ricinoleic acid, an omega-9 that is unique to it. This is complemented by other fatty acids as well as vitamin E.

There are numerous beneficial effects of castor oil on the skin. Its moisturising, nourishing and emollient properties give it its hydrating power, perfect for dry skin. The castor oil also has virtues for the hair and helps to strengthen hair fibres while stimulating their growth.

A tanned and golden skin is the result of the action of the sun's UV rays which stimulate the melanogenesis process in the skin, leading to the synthesis of melanin, the brown pigment that colours it. It's worth noting that this is actually a defence mechanism set up by the skin. Indeed, UV rays generate free radicals in cells that damage cell membranes, but also DNA, which can lead to mutations and the formation of cancerous cells. That's why it's important to generously apply sunscreen before exposing yourself to the sun.

Regarding the properties of castor oil, there is currently no study that concludes this ingredient stimulates tanning. Furthermore, among the molecules present in its composition, none seem to have the ability to influence melanogenesis. It's also worth noting that applying castor oil before sun exposure will not accelerate tanning. Without sun protection, it is more likely to cause redness and sunburn. Therefore, at this time, castor oil cannot be considered a tanning vegetable oil.

Even though castor oil has no effect on tanning, this does not mean it is not a valuable ally when exposed to the sun. Indeed, among its many benefits, the following properties are particularly useful when one is sunbathing.

• Castor oil has antioxidant properties.

  Castor oil contains tocopherols (vitamin E), which are potent antioxidants. Antioxidants protect the skin from oxidative stress caused by UV rays. Notably, vitamin E is capable of transforming hydrogen peroxide (H₂O₂) into water (H₂O), before it can damage cells. Regular application of castor oil thus has a photoprotective effect and helps to limit the damage that UV rays can cause.

• Castor oil helps to maintain the hydrolipidic film.

  The oleic (omega-9) and palmitoleic (omega-7) acids found in castor vegetable oil have a protective effect on the skin. Indeed, these compounds are naturally present in the hydrolipidic film. This film is located on the surface of the epidermis and notably helps to protect it from UV rays, pollution, and dehydration. The sun has a drying effect on the skin and tends to weaken this film. Applying castor oil after sun exposure helps to recreate the hydrolipidic film.

• Castor oil helps to restore the skin barrier.

  Castor vegetable oil also contains linoleic acid, a compound capable of reacting with the ceramides of the stratum corneum. This esterification reaction allows the linoleic acid to bind with these lipids, forming the skin's impermeable barrier. However, this barrier is disrupted after exposure to the sun, which increases water loss. Therefore, applying castor oil afterwards proves to be beneficial.

Important : despite its oily texture which may suggest otherwise, the castor oil can in no way replace a sunscreen as it does not contain any UV protective filters.

• MARWAT S. K. & al. Review - Ricinus communis - ethnomedicinal uses and pharmacological activities. Pakistan Journal of Pharmaceutical Sciences (2017).