There is a lack of qualified studies on black castor oil and its effect on human hair.

There are, however, many people who, supported primarily by anecdotal evidence, feel that using black castor oil on their hair promotes hair health and hair growth.

Derived from the seeds of the castor bean (Ricinus communis), castor oil has industrial applications as a lubricant as well as use as an additive in cosmetics and foods. It is also used medically as a stimulant laxative.

Containing high amounts of ricinoleic acid, an omega-9 fatty acid, castor oil has, according to a 2012 study, antioxidant, antimicrobial, and anti-inflammatory properties.

There are two types of castor oil generally available:

  • yellow castor oil, made by cold pressing fresh castor beans
  • black castor oil, made by roasting the castor beans and then using heat to extract the oil

Because the method of starting with roasted beans was developed in Jamaica, black castor oil is often referred to as Jamaican black castor oil.

One way that proponents of black castor oil support their position is by aligning it with the benefits of other essential oils.

Although there are indications that many oils, such as peppermint oil (according to a 2014 study) and lavender oil (according to a 2016 study), have potential as hair growth-promoting agents, there is a lack of qualified studies on black castor oil and its effect on human hair.

Castor oil is a natural humectant (retains or preserves moisture) often used in cosmetics — added to products like lotions, makeup, and cleansers — to promote hydration.

Advocates of castor oil for hair and skin suggest that its moisturizing properties translate to hair and scalp health as well. Those who want to avoid the scents, dyes, and preservatives often found in commercial cosmetics, use it in its original undiluted form or mix it with a carrier oil, such as:

According to Toxnet Toxicology Data Network, castor oil could cause mild irritation and discomfort to the eyes and skin.

Although small doses of castor oil are considered safe in small oral doses, according to a 2010 study, larger amounts can result in:

Pregnant women should not take castor oil by mouth.

As you should do with any new topical product, test a tiny amount of black castor oil on your inner arm. After applying it, wait 24 hours to see if there is any sign of irritation.

Castor beans naturally contain the poison ricin. If you chew and swallow castor beans, ricin can be released and cause injury. Ricin is also in the waste that is produced in the manufacture of castor oil. Castor oil does not contain ricin.

The Centers for Disease Control and Prevention (CDC) suggests that it is highly unlikely to be intentionally exposed to ricin unless you were to actually eat castor beans. The CDC also indicates that ricin has been the focus of medical experiments to kill cancer cells.

Without recognized clinical evidence, there is only informal anecdotal narrative to suggest that black castor oil can promote hair growth and yield other healthy hair benefits.

If you decide to experiment on your hair with castor oil, consult your doctor first. They should be able to outline any concerns about castor oil affecting your current health status, including any potential interactions with medications or supplements you’re currently taking.