Castor oil allegedly was a weapon in Cleopatra's beauty arsenal - the Queen of the Nile is said to have used it in her hair and, some sources say, to brighten the whites of her eyes. Picture: Supplied

Washington - Castor oil has been around for thousands of years and has been a medicine-cabinet staple for hundreds. 

So it's somewhat surprising to see the standby elixir - known for calming stomachs and beautifying hair - gaining attention from the wellness and beauty industries that are churning out products claiming to grow your eyelashes or make your skin glow.

Domesticated in Eastern Africa and introduced to China from India an estimated 1 400 years ago, the castor oil plant is one of the oldest cultivated crops in human history. Castor oil allegedly was a weapon in Cleopatra's beauty arsenal - the Queen of the Nile is said to have used it in her hair and, some sources say, to brighten the whites of her eyes. 

What is castor oil?

Castor oil is made by pressing the seeds of castor beans, which yields a viscous liquid thicker than olive oil and pale yellow in hue. Known for being full of triglycerides and fatty acids, castor oil contains a high volume of ricinoleic acid, a versatile component that makes it well-suited to a wide range of formulas - industrial, medical and pharmaceutical alike. Castor oil's benefits are myriad: as a moisturizer and anti-inflammatory, as well as a hair thickener and strengthener.

Why now?

Castor oil has historically appeared in many products, though until recently only a few brands featured the ingredient front and centre. 

Now it's being marketed on the front of product packaging instead of buried in an ingredient list under its chemical name, according to Manhattan-based dermatologist Julie Russak. She sees a couple of wellness trends at play in the ingredient's newfound fame.

"Basically, companies are calling out natural ingredients right now because that is what consumers are looking for," Russak said. Castor oil "has longevity. It's not a chemical product that has just been designed in the lab."

In addition, she said, "Oils in general are having a comeback, and castor oil is getting a rebrand. We talk about eating good fats, eating fatty acids, oils, fish oils, different triglycerides, getting them out of avocados, for the inside. But oils are the answer for that on the outside."

What about those beauty claims?

Advertising claims aside, at least one study has shown that castor oil increases hair luster - more commonly understood as shine - overall, according to Bindiya Gandhi, a physician who practices functional and integrative medicine in Georgia. 

Though there are no studies that show castor oil directly causes hair growth, Gandhi said, the theory isn't far-fetched. "Hair growth is triggered by prostaglandin (PGE2) and ricinoleic acid in castor oil has been shown to stimulate PGE2 so we can conclude that this is the reason that it increases hair growth," she wrote in an email. She gives the example of Latisse, an eyelash growth product that uses the "same mechanism of action."

Gandhi remembers her mother using castor oil on her hair when she was a child, as well as giving it to her orally for constipation. When she had her own daughter last year, she reached for it, too.

"Topically, you're getting anti-inflammatory properties," Gandhi said, which is why castor oil is an ingredient in products such as anti-aging and stretch mark creams and ointments for sunburns and rashes. Castor oil also can be used as an antibacterial and antifungal treatment to combat yeast overgrowth and buildup on the scalp.

At the same time, she cautioned, a little bit of castor oil goes a long way - and it's not right for everyone or everything.

The Washington Post