What are the side effects of black seed oil?

For thousands of years, black seed, known also as black cumin and black caraway, has been used as an herbal remedy in traditional medicine. Presently, science is still trying to prove black seed oil’s potential benefits and therapeutic role in modern medicine, and of equal importance, research is needed on its safety. Preliminary studies have fueled hope for its use in various health conditions, including allergies, infertility, high blood pressure, diabetes, cancer, and weight loss for obesity. While those applications still need to be confirmed, the evidence of black seed oil’s side effects is being uncovered, too. We will update you on what we currently know.

Common side effects of black seed oil

The chance of having an adverse effect from taking black cumin seed oil is largely undefined. Gastrointestinal symptoms with oral ingestion and skin and nasal reactions to topical application seem to be most common.

• Nausea and vomiting
• Abdominal bloating
• Abdominal pain
• Nasal dryness
• Rash

Serious side effects of black seed oil

Limited research and isolated case reports have raised concern for possible side effects of a severe nature from the use of black seed oil. Other researchers have not confirmed these severe side effects.

• Allergic reactions
• Hypoglycemia (low blood sugar levels)
• Elevated liver enzymes
• Kidney function decline
• Bleeding
• Overdose toxicity

How soon do black seed oil side effects start?

The onset time of adverse reactions to black cumin seed oil has not been elucidated to date. Based on the short timeframe of most studies on black seed supplements, an onset within days to weeks would be predicted. Long-term, large-scale clinical studies are needed to establish this, however.

How long do black seed oil side effects last?

Clinical trials have not firmly nailed down the duration of side effects from black cumin oil after the herbal remedy is stopped. Extrapolating from other medications with similar side effects could provide a reasonable guesstimate. Typically, drug-induced hypoglycemia resolves within hours and skin and intestinal symptoms improve within days of stopping an inciting drug. 

What are the long-term side effects of black seed oil?

The most alarming findings bring up kidney and liver toxicity questions. No proof exists to substantiate those worries, but if black seed oil truly can cause harm to these organs, the potential exists for some degree of permanent damage.

Who should not take black seed oil?

Some would question whether any individuals should take black seed oil since it has not been sufficiently tested with peer-reviewed, placebo-controlled studies and is not approved for use by the Food and Drug Administration (FDA). Nonetheless, most would agree that until the serious adverse effect concerns are refuted, the following conditions could be considered contraindications to black seed oil.

• Pregnancy
• Upcoming surgery
• Anticoagulant therapy or high risk of bleeding
• Advanced kidney disease
• Advanced liver disease
• Hypoglycemia (low blood sugar) risk
• Hypotension (low blood pressure) risk

Black seed oil warnings

Based on findings thus far, people with a history of bleeding, hypoglycemia, hypotension, renal impairment, or hepatic impairment should avoid black seed oil or at least discuss it with their healthcare provider prior to starting, although this is advisable for everyone. 

If black seed oil is taken, dosing decisions could be very important. Animal studies have found high doses to be toxic and life-threatening. High-quality human studies are still needed.

Dosing guidelines have not been established, so it is difficult to determine starting, typical, and maximum doses. Studies have often used 1 to 2 grams per day of product from the seeds of Nigella sativa and limited duration to 3 months or less.

Black seed oil interactions

• Black seed oil can interact with medications for diabetes mellitus by amplifying the risk of hypoglycemia. Additional blood sugar monitoring may be necessary.
• Taking black seed oil concurrently with antihypertensive drugs could result in hypotension. Watching for symptoms of lightheadedness and checking for lower blood pressure readings could be advised.
• Anticoagulants coupled with black seed oil could magnify the risk of hemorrhage.
• The cough suppressant dextromethorphan was not metabolized as readily when taken with black seed oil in a study. This interaction could lead to higher levels of the drug and more adverse effects. The cause was noted to be black seed-inhibited CYP3A4 and CYP2D6 enzyme metabolism.
• The findings of impeded CYP3A4 and CYP2D6 enzyme metabolism by black seed have created concern that other drugs could be affected too. This could mean that black seed oil interacts with numerous meds, including some from such common drug classes as calcium channel blockers, macrolide antibiotics, and statins.
• Drug levels of sildenafil, cyclosporine, and phenytoin were reduced when taken concurrently with black seed oil. As a result, the drugs could be ineffective, a dangerous proposition considering that cyclosporine is an immunosuppressant and phenytoin is an anticonvulsant.

How to avoid black seed oil side effects

1. First and foremost, before starting an N. sativa plant product for any of your medical conditions or for a protective effect, ask your healthcare provider if you should take this supplement, what potential negative or positive effects you may experience, and what dosing or monitoring is advised.
2. Monitor your blood glucose when taking black seed oil.
3. Monitor your blood pressure when taking black seed oil.
4. Black seed oil can be taken with food, which could reduce stomach upset.
5. Limit intake to no more than 2 grams of black seed oil per day and duration to no more than 3 months.
6. Recognize the potential side effects of this herbal dietary supplement, including rash, abdominal pain, and bleeding, and discontinue it immediately if any are noted.
7. Avoid black seed oil if you take blood thinners or have a history of bleeding, hypoglycemia, hypotension, or advanced kidney or liver disease.
8. Pregnant women should avoid products from the seeds of the Nigella sativa plant.
9. Take your list of prescription drugs and over-the-counter meds, remembering to report any dietary supplements as well to your medical team of providers and pharmacists, and ask them if one could interact with black seed oil, specifically if any are CYP2D6 or CYP3A4 substrates.
10. If you are looking into alternative medications due to cost concerns with your prescriptions, try a SingleCare discount card to see how much money you could save.

How to treat side effects of black seed oil

Considering the unproven benefits of the oil from these tiny black seeds, any side effects that are experienced should lead to its discontinuation. You should then call your doctor to ask if any other actions are recommended to alleviate symptoms of the adverse reaction. Treatment may be available for nausea, bloating, or skin irritation. Quick-acting sugary food or drink could correct hypoglycemia. If the side effects of black seed oil are severe, such as in the case of bleeding, you should seek emergency medical attention. Before and during the use of any supplement, communication with your care providers is key.