The use of castor oil can be traced back all the way to the ancient Egyptians, who used it as an ointment. Today, this oil is popular as a hair care product, said to improve hair growth and appearance. Read on to explore all the potential health benefits of castor oil and the science that backs it up.
What Is Castor Oil?
Castor oil is a pale yellow vegetable oil derived from the castor bean plant – Ricinus communis. While different parts of the plant have specific health benefits, the bean of the plant is the most commonly used [R, R].
The castor bean plant has a long history as a traditional remedy. It was used by the ancient Egyptians as an ointment for wounds, and by the Greeks and Romans as a laxative. In south India, both castor oil and coconut oil are used for oil baths to nourish the skin and promote hair growth. Today, castor oil can be found in medicine, cosmetics, soap, and even biodiesel [R+, R, R, R].
The process of growing and manufacturing this oil is challenging. One issue is that castor plant seeds contain a substance called ricin, which is extremely toxic [R].
- All natural product
- May improve hair growth and appearance
- May help with wound healing
- May reduce inflammation
- May fight bacteria
- Can be mixed with other oils for hair care
- Relieves constipation when ingested
- Thick consistency makes handling difficult
- Strong odor
- Can cause skin reactions
- Mild side effects are common if ingested
- Should not be ingested by pregnant women (it can induce labor)
Components of Castor Oil
Castor oil contains a unique compound called ricinoleic acid, which makes up 90% of the fat in the oil. Ricinoleic acid is an unsaturated fatty acid that is responsible for many of castor oil’s health effects [R, R].
On the downside, it’s also very thick and hard to wash out if used alone. For this reason, it’s often combined with other lighter oils, such as coconut oil, or even with the slightly thicker antioxidant-rich olive oil. It can also be combined with aloe vera or with aromatic, anti-inflammatory essential oils, like those of star anise, oregano, or black seed [R, R, R].
The poisonous compound ricin is found inside the seeds of the castor plant. However, the oil extraction process removes all ricin from castor oil [R].
Jamaican Black Castor Oil vs. Regular Castor Oil
Jamaican black castor oil is unique because it contains ash, which is a byproduct of the bean roasting process. The ash makes the oil less sticky and easier to apply.
Jamaican black castor oil is purported to have many of the same hair benefits as regular castor oil. However, there are no scientific studies supporting these claims.
The vitamin E in Jamaican black castor oil is also believed to improve skin health and is used for healing wounds.
Both types of oils are sold commercially in stores and online.
How Can Castor Oil Improve Hair and Skin Health?
Many factors can trigger hair loss. However, high levels of an enzyme called prostaglandin D2 synthase are one of the culprits, especially in men. High levels of an inflammatory substance this enzyme produces – prostaglandin D2 (PGD2) – are linked to blocked hair growth and baldness. In fact, mice with high PGD2 levels develop baldness and oily skin. What’s more, slightly higher levels are also linked to slower hair growth [R, R].
Scientists consider that blocking PGD2 may hold the “cure” for hair loss and baldness. Blocking it may also speed up skin regeneration, while high PGD2 levels block skin repair mechanisms. This would be equally important for scalp health [R, R, R]. So where does castor oil come into the picture?
As mentioned, ricinoleic acid is the most active component in the oil. Interestingly, this fatty acid may target precisely prostaglandins. Although studies have not confirmed its direct effect on hair loss, ricinoleic acid blocked the enzyme that makes PGD2 in a lab setting. Additionally, castor oil has anti-inflammatory, antioxidant, microbe- and yeast-killing properties, all of which can enhance hair and skin health [R, R, R].
Skin & Hair Use
1) Hair Care & Moisturizing
Because of its moisturizing properties, castor oil is popular as a natural hair conditioner. It is also said to promote hair growth, improve texture, and reduce dandruff. However, very little research exists to support these claims.
As mentioned above, one of the main ways this oil works is probably by blocking PGD2, high levels of which have been linked to hair loss and oily skin. And unlike some other oils, ricinoleic acid from castor oil has a low potential for adverse skin reactions [R].
One image analysis looked at the effect of various cosmetic products on hair samples. Similar to other cosmetic oils, castor oil was found to increase hair luster [R].
2) Wound Healing
Several studies have looked at using castor oil for pressure ulcers, skin wounds caused by prolonged pressure or friction. They found that ointments that include castor oil can shorten healing time [R, R].
One study of 36 people used an ointment containing castor oil and balsam of Peru, a type of tree sap. This ointment healed skin graft wounds within 11 days with no reported complications [R].
Research also examined castor oil’s effect on melasma, a skin condition that causes dark patches to appear on the face. A skin peel containing castor oil and phenol successfully reduced skin discoloration in 30 patients [R].
3) May Help with Skin Inflammation
Castor oil has anti-inflammatory and antioxidant effects. Ricinoleic acid reduced inflammation in mice and guinea pigs when given orally, which also may explain its beneficial effects on skin inflammation. Flavonoids in the oil probably carry its antioxidant, free radical-scavenging properties [R, R, R, R].
4) Fights Bacteria and Yeast
Castor oil has the potential to be used as an antiseptic skin cleanser in solutions. In one study, castor oil killed numerous bacteria, including those that commonly cause skin infections. It was also active against Candida and a type of fungus that causes allergic diseases [R, R].
Additionally, yeast that cause dandruff and eczema can feed on many common oils, but most of them can’t take in castor oil. As a result, it’s possible that castor oil may stop the growth of these skin disease-causing fungus, but so far the data are limited [R, R].
In another study, a solution of castor oil and sodium hypochlorite was an effective antiseptic. The solution is able to fight multiple bacterial species and may be useful for cleaning dentures. It’s important to note that sodium hypochlorite is a known antiseptic, so the contribution of castor oil in this study is unclear [R].
5) Reduces Pain From Shock Therapy
Shock wave therapy is used in certain bone conditions. A lubricating substance, like vaseline or ultrasound gel, is applied to the skin to aid with the therapy [R].
One study evaluated 60 people with bone conditions who received shock wave therapy. Compared to vaseline and ultrasound gel, castor oil was significantly better at reducing pain [R].
How To Use
Castor oil is very thick and can be difficult to wash out. If you’re going to apply it alone, use only a small amount on the scalp. Make sure not to saturate your scalp or hair with the oil to avoid hair matting or not being able to wash it out. Don’t use very hot water to wash the oil out, use lukewarm water instead [R].
Jamaican castor oil may be easier to apply and wash out due to its ash content, but this is based only on anecdotal information. It’s safer to apply it sparingly and cautiously.
Instead of using castor oil alone, a much better solution is to combine a small amount with less viscous oils, such as [R]:
- Coconut oil
- Olive oil
- Sesame oil
- Avocado oil
- Almond oil
You can also combine it with aloe vera, which is rich in vitamins and antioxidants.
Another great option is to add some essential oils to the mix, either to enhance hair health or for a relaxing effect. The following oils may be beneficial [R]:
Note: Some people are allergic to castor oil. To avoid a dangerous reaction, test out a small patch of skin or scalp first to see how you will react.
Because it blocks the enzyme that stops hair growth, it’s possible that castor oil may also enhance the growth of eyebrows and eyelashes. However, the area around the eyes is extremely sensitive and we caution against using castor oil on the face in general to avoid any possible irritation. If you’ve already used castor oil or tested out your reaction on a small skin area, you may try using a couple of drops on your eyebrows. For eyelashes, it’s safer to avoid it altogether [R].
Side Effects & Precautions
Castor oil can cause an allergic skin reaction called contact dermatitis. It is not considered a significant skin irritant but may cause irritation in susceptible individuals [R].
A case-study looked at the effects of hairspray that contained castor oil. During a two-year period, 12 cases of dermatitis were reported [R].
Users should be aware that castor oil has a very thick consistency when used alone. In one case, a woman developed severe hair matting after using oil baths with coconut and castor oil. Hair matting occurs when the hair becomes severely twisted and entangled [R].
Coconut oil alone is easy to wash out. If using both, make sure that you mix in only a small amount of castor oil. It’s also crucial not to use very hot water and too much friction when washing it out, as both can cause hair to permanently stick together and tangle. This is probably what triggered hair matting in the case mentioned above [R, R].
Aside from its use for hair and skin care, castor oil may be ingested, mainly for its laxative effects. Research about its potential to reduce inflammation and fight cancer is very limited. Additionally, its oral use is linked to some side effects we cover in more detail below.
1) Constipation Relief
Castor oil has a rich history as a laxative, with reports of its use dating back to ancient Egypt [R].
One study evaluated castor oil in 35 elderly patients who suffered from chronic constipation. It was effective at decreasing strain and the feeling of an incomplete bowel movement [R].
Before some procedures, like a colonoscopy, laxatives are required to empty the colon. Studies show castor oil is just as effective as other drugs for this purpose. However, in one of these studies about 28% of people experienced side effects while taking castor oil [R, R, R].
2) Arthritis Symptoms
A clinical trial of 100 people found that castor oil may be effective for those that suffer from arthritis in the knee. According to this study, castor oil capsules were just as effective as diclofenac, a commonly used NSAID, at relieving symptoms. No side effects were reported with castor oil use [R].
Castor oil blocks the growth of tumors in mice with cancer. A cell study shows that tumor cells are sensitive to a toxic lectin, which is derived from castor oil. Clinical studies have not examined these effects and it’s impossible to say if castor oil has any cancer-fighting effects in people [R, R].
According to the Food and Agricultural Organization and World Health Organization, up to 0.7 mg/kg of castor oil orally per day is safe. There is not enough data to determine the optimal dose of castor oil for specific conditions [R].
Side Effects & Safety
Castor oil is recognized as being generally safe for use as a laxative by the FDA [R].
The side effects are mainly caused by its effect on bowel movement. Studies have reported differing side effect frequencies. According to one study found, about 28% of people experience side effects [R, R].
Common side effects of castor oil include [R]:
- Stomach cramps
In addition, the laxative effects of castor oil can be undesirable for certain uses.
Castor oil is known to cause contractions and induce labor in pregnant women. For this reason, the FDA recommends that castor oil should NOT be taken during pregnancy. It should only be used under the supervision of medical professionals [R].
The seed of the castor plant contains a protein named ricin that is extremely toxic. It blocks activity in the cells, which can quickly lead to death [R].
Luckily, castor oil does not contain ricin. The oil extraction process should remove ricin from the oil. The only documented cases of ricin poisoning come from people who have ingested the castor bean [R, R, R].
Does Castor Oil Induce Labor?
Castor oil has long been traditionally used to induce labor in pregnant women. In recent years, its popularity has declined due to concerns about safety and effectiveness. This is due to the mixed results of scientific studies [R, R].
Some scientists think that this oil should be researched further to help women initiate labor. It’s a cheap herbal option used for this purpose mostly in developing countries. However, there’s some interesting research behind it.
However, one very recent study found that women who received castor oil had a higher chance of birth within 24 hours. In another study of 323 women taking the oil, almost 91% gave birth without any complications [R, R].
Similarly, a recent clinical trial of 81 women showed that castor oil is effective for overdue pregnancies. It induced labor in these late pregnancies within 24 – 48 hours, but only in women who had given birth before. It was not associated with any pregnancy complications or safety risks. However, one review did find that all the women who took the oil became nauseous [R, R, R, R].
In addition, there is a case report where a woman experienced stomach pain and uterine rupture shortly after taking castor oil. Changes to the baby’s heart rate eventually prompted a C-section delivery [R].
If you’re pregnant, it goes without saying that you shouldn’t be using castor oil without medical supervision.
Limitations and Caveats
Research on castor oil and its effects in humans is very limited. In addition, most studies looking at safety have been performed in animals. This makes it difficult to fully evaluate its effect in humans [R].
Reviews of castor oil are generally positive. Many use castor oil for hair and skin care. Users state their hair grows faster, shinier, and stronger. In addition, some users say it noticeably reduces the amount of acne and wrinkles.
Negative reviews frequently mention the strong smell. Multiple users have compared the oil’s scent to cigarettes. Others have complained about its thick consistency and stickiness.
Buy Castor Oil
Castor oil is a vegetable oil derived from the castor bean plant. Since ancient times, it has been used as an ointment and laxative.
Nowadays, castor oil is popular as a cosmetic product. It is said to improve hair growth and appearance. It is also sometimes used on the skin to reduce acne and wrinkles.
Castor oil has many reported benefits, but few are supported by strong evidence. Current research suggests it may block pathways linked to hair loss. It’s safe when used on scalp or skin, but some people may be allergic to it. It may also cause hair matting when used in large quantities.
If applying this oil to the hair, use it sparingly and cautiously. Consider mixing small amounts with lighter oils that are easier to wash out (like coconut oil) and avoid rinsing with very hot water.
Despite the lack of evidence, many users have had positive experiences with castor oil as a hair product. It could be an option for dry, damaged hair as long as you can get past the oil’s stickiness and strong smell.
When ingested, castor oil can cause stomach-related side effects.