Black seed has many traditional uses and can be taken as a spice, extract, or oil. Despite being touted as a “miraculous herb,” many of its traditional uses have not been validated by proper scientific studies. Read on to learn more about the potential side effects of black seed oil and how to safely use it.
What is Black Seed Oil?
Nigella sativa, commonly known as black seed, black caraway, and kalonji is a flowering plant native to South Asia. Its fruit is large and contains numerous small black seeds .
Black seed is also sometimes called black cumin (or black cumin seed), although this can be misleading. Cumin or Cuminum cyminum is a spice with few overlapping benefits that belongs to an entirely different plant family than black seed.
In this article, any mention of black seed or black cumin refers specifically to Nigella sativa.
Nigella sativa raw seeds, seed oil, or seed extract have been traditionally used alone or in combination with other ingredients for various health conditions, such as eczema, cough, headache, diabetes, asthma, infections, and high blood pressure .
Few of the claims that come from its traditional reputation in various cultures have been researched, while most others lack scientific evidence and rely on findings from studies in cells or animals .
Specifically, some evidence suggests that black seed oil may be beneficial in people with diabetes, asthma, high blood pressure, male infertility, and breast pain. Other purported benefits of black seed oil haven’t been sufficiently studied.
Additionally, black seed supplements have not been approved by the FDA for medical use. In general, dietary supplements lack solid clinical research. Regulations set manufacturing standards for supplements but don’t guarantee that they’re safe or effective. Speak with your doctor before supplementing.
What Does Black Seed Oil Do?
Black seeds have been used in Middle Eastern, Asian, and European folk medicine as a natural remedy for a wide range of diseases for over 2000 years .
In Islamic cultures, its use has a strong religious background. Islamic literature claims that regular use of black seed is “a cure for every disease (except death),” which earned this spice the Arabic approbation “The Blessed Seed.” Black seed is also considered an important remedy in Ayurveda .
Black seed has a specific bitter taste and smell and is often added to confectionery and liquors. The oil can be used to add flavor to various dishes, but people also traditionally apply it on the skin as an alleged painkiller and antiseptic.
Despite its cultural significance, the traditional uses and purported health benefits of black seed remain unproven.
Black seed is a source of the following nutrients:
- Fatty acids, which make about 30% of the seeds. These are mostly unsaturated fatty acids, including linoleic acid and oleic acid, and some saturated fatty acids .
- Various vitamins and minerals, such as copper, phosphorus, zinc, iron, beta-carotene (provitamin A), thiamin (B1), niacin, folic acid, and (Vitamin B6) 
Active Ingredients Research
The main and most researched active ingredient in black cumin seed oil is thymoquinone. Thymoquinone has been studied for protecting the liver, reducing inflammation, and as an antioxidant. It’s also being examined in cancer research. Additionally, the seeds contain alpha-Hederin, another ingredient that’s being studied in cancer cells [2, 5].
The following molecular targets have been identified by scientists in cell-based and animal studies. They do not translate to health benefits but help guide further research.
- Decreases LOX (Lysyl Oxidase) 
- Inhibits iNOS (inducible Nitric oxide synthase) 
- Inhibition of NF-κB (NF-kappa B) 
Proposed Anticancer Properties
- Activates PPAR-γ (Peroxisome proliferator-activated receptor gamma) 
- Increases PTEN (Phosphatase and tensin homolog) 
- Increases BAK/BAX 
- Decreases Bcl-2 and Bcl-xL 
- Suppresses the expression of AR and E2F-1 
- Increases the activity of Myeloperoxidase, Glutathione-S-transferase, Adenosine deaminase 
- Increases enzymes like Superoxide dismutase (SOD), Catalase and Glutathione peroxidase 
- Increases GABA (Gama Amino Butyric Acid) activity 
Activity in the Lungs and Trachea
Black Seed Oil Side Effects & Precautions
This list does not cover all possible side effects. Contact your doctor or pharmacist if you notice any other side effects.
Proper safety trials with black cumin seed oil and its active ingredients have not been carried out. Limited evidence suggests that black seed is safe when used as a spice .
Pregnant women should avoid taking black cumin seed extract or oil.
Black cumin seeds can cause abortions in larger amounts . Also, clinical studies have not confirmed that it is safe to use in pregnancy even in smaller amounts or in children.
Reported Side Effects
Although black seed oil is generally thought to be safe, several rare cases of skin allergies to the oil have been reported. These reactions are more common when black seed oil is applied to the skin .
The following side effects have also been reported in people using black seed oil by mouth:
- Gut-related complaints (constipation, burning, discomfort, vomiting, and nausea)
- Worsening of seizures
Sudden kidney damage (acute renal failure) has been described in one case report of a 62-year-old woman with diabetes using black seed tablets (2-2.5 g daily) .
Although there are no other reported cases of black seed oil causing kidney-related side effects, caution is advised, particularly in people with diabetes and/or kidney disease.
Since black seed may excessively reduce blood sugar levels and blood pressure if taken with medications for high blood pressure or diabetes.
In theory and based on its possible health effects, black seed oil may also interact with blood thinners, sedatives, immune-suppressants, and diuretics.
Have in mind that herb-drug interactions can be dangerous and, in rare cases, even life-threatening.
Always consult your doctor before supplementing and let them know about all drugs and supplements you are using or considering.
How to Use Black Seed Oil
Because black seed oil is not approved by the FDA for any condition, there is no official dose. Users and supplement manufacturers have established unofficial doses based on trial and error.
A typical dose of the oil, recommended by most manufacturers, is 2.5 – 5 ml 2X daily.
As crushed or powdered seeds, the dosage is typically about 1 g per day.
Discuss with your doctor if black seed oil may be useful as a complementary approach in your case and which dose you should take.
Scientists are exploring whether garlic extract and black cumin seed oil may work better together to combat parasites .
Black cumin seed and garlic together may work together to lower high cholesterol, though the evidence is inconclusive .
Consumption of garlic extract and crude black cumin may have beneficial antioxidant effects in healthy postmenopausal women .
Most people use black seed oil for general wellness and to boost energy. We came across several reviews that mention the oil is good for immune support, seasonal allergies, and cold prevention. But since it has an unpleasant taste and triggers a burning sensation, most users recommend combining it with orange juice, tea, or adding it to smoothies.
Some users tolerate black seed oil well and report only mild nausea or stomach upset at first. Others, however, seemed to struggle with serious gut-related side effects like vomiting, diarrhea, and subsequent dehydration.
Among less common side effects, users also mention liver pain and chest pain.
One person who took black seed oil for libido enhancement didn’t experience any benefit. On the contrary, their mood worsened and they stopped taking the oil.
People who take black seed oil for hair growth and skin health are mostly happy with the results, though headaches and itching are frequent complaints.
Black seed or Nigella sativa is a flowering plant with a long history of traditional use, particularly in the Middle East. It should not be confused with cumin, a completely different spice with distinct potential health benefits.
Black seed is thought to be generally safe when used in amounts found in food, but skin allergies and gut complaints have been reported. It may also cause uterine contractions, which is why pregnant women should avoid it. Be sure to consult your doctor before supplementing.