Black Seed Oil (Nigella sativa)

What it is

Black seed is the small black seed of Nigella sativa, a flowering plant grown from the Mediterranean to India. It's also sold as black cumin or kalonji, and it has been used as food and medicine across the Middle East and South Asia for over two thousand years. Pressing the seed gives black seed oil.

The compound that matters most is thymoquinone (TQ), which makes up a small fraction of the oil but accounts for most of its effects. The seed also carries related compounds (thymohydroquinone, nigellone, carvacrol), and the oil itself is mostly fat: about 50–60% linoleic acid and 20–25% oleic acid.

How it works

Thymoquinone does five things that show up again and again across tissues. Nearly every benefit below is one of these five at work in a different organ.

• It turns down inflammation. TQ suppresses NF-κB, the master switch that tells cells to make inflammatory signals. With that switch turned down, cells make less TNF-α (the signal that drives tissue damage in rheumatoid arthritis and inflammatory bowel disease), less IL-1β and IL-6, and less IL-5 and IL-13, which drive allergy and asthma. TQ also blocks COX-2 and 5-lipoxygenase, the enzymes that make prostaglandins and leukotrienes. COX-2 is the enzyme aspirin and ibuprofen block for pain relief.
• It turns up the body's own antioxidants. TQ activates NRF2. When NRF2 is switched on, it moves into the cell's nucleus and tells the cell to make its own protective enzymes: superoxide dismutase, catalase, heme oxygenase-1 and the enzymes that make and recycle glutathione. That lasts longer than an antioxidant that just mops up free radicals directly.
• It steadies the immune system. TQ affects how T cells and B cells multiply and activate. When the immune system is overactive, as in autoimmune disease, it reins in excess IL-2 and T-cell activation. In healthy people it supports helper T cells. The net effect is balance, not a simple boost or brake.
• It improves how cells handle fuel. TQ activates AMPK, the cell's low-fuel sensor. AMPK turns down mTOR, which frees the cell to clean out worn parts (autophagy). TQ also raises GLUT4, the transporter that pulls sugar out of the blood and into muscle, and in rats it slows HMG-CoA reductase, the liver enzyme that makes cholesterol and that statin drugs block.¹
• It pushes damaged cells to self-destruct. In abnormal and cancerous cells grown in the lab, TQ disrupts the PI3K/Akt growth pathway and destabilizes the mitochondria. That releases the signals (Bax, caspases) that trigger apoptosis, the body's orderly way of clearing cells beyond repair. Healthy cells are far less affected. This is lab work: no human studies have tested black seed as a cancer treatment.

Cellular energy: NQO1 and NAD⁺ recycling

Thymoquinone is a quinone, which makes it fuel for an enzyme called NQO1. NQO1 does two useful things in one step. It converts NADH back into NAD⁺, which mitochondria need to keep burning fuel. And it turns the quinone into a form that works as a recyclable antioxidant. NQO1 does this cleanly, without creating the unstable radical that other enzymes produce when they handle quinones.

TQ isn't the only compound that feeds this enzyme. CoQ10, PQQ and beta-lapachone (from Pau d'arco) do the same. NQO1 itself is switched on by NRF2, so anything that activates NRF2, such as exercise or sulforaphane from broccoli, supports the same pathway.

TQ also activates AMPK and SIRT1, the energy-sensing pathways that fasting and exercise switch on and that are tied to healthy aging. In aged rats, TQ restored SIRT1 activity and reversed age-related damage in tissue.² No human studies have measured these pathways after taking black seed. (Well-established enzyme chemistry; animal and cell studies for the aging pathways)

Blood sugar, cholesterol and blood pressure

This is the most-studied use. A 2025 analysis pooled 82 trials with 5,026 people, using 200 mg to 4.6 g a day for up to 48 weeks. Black seed improved fasting blood sugar, HbA1c, insulin sensitivity, LDL, triglycerides, HDL, blood pressure, body weight and waist size.³

The effects are modest, and the individual trials are small. The mechanism fits. AMPK tells the liver to make less glucose, GLUT4 moves more sugar into muscle, and less inflammation improves how cells respond to insulin. Slowing the liver's cholesterol-making enzyme would explain the drop in LDL (for what LDL does and doesn't tell you, see Statins & LDL).

Black seed also lowers leptin and insulin. In 46 overweight women, about ½ tsp (2 g) of black seed oil a day for eight weeks lowered leptin, insulin and the inflammatory signals IL-1β and IL-6, compared with placebo.⁴ High leptin with high insulin is the usual pattern in people carrying excess fat, so both falling together is a sign of better metabolic health. Black seed belongs alongside diet, not in place of it (see Metabolic Health).

Allergies, asthma and histamine

Allergy symptoms come from mast cells, which release histamine and leukotrienes when they meet an allergen. Black seed works on both. Thymoquinone and nigellone steady mast cells so they release less histamine, and TQ blocks 5-lipoxygenase, the enzyme that makes leukotrienes. Leukotrienes are what tighten the airways in asthma.

The human trials agree. Across 8 hay-fever trials, people taking black seed were about four times as likely to get relief, with fewer nasal symptoms.⁵ Across 4 asthma trials, asthma-control scores and lung function improved.⁶ In a trial of a standardized oil (5% thymoquinone), nasal and eye symptoms both eased within 15 days.⁷ That trial was run by the oil's manufacturer.

Inflammation and oxidative stress

Across 20 trials with 1,086 people, black seed lowered C-reactive protein and TNF-α, two standard blood markers of inflammation. It also lowered MDA, a marker of fat oxidation, and raised the body's own antioxidant enzymes, superoxide dismutase and glutathione peroxidase.⁸ That matches the two core mechanisms above: less NF-κB activity and more NRF2 activity.

Because it blocks COX-2, black seed has been used for joint pain in the way anti-inflammatory painkillers are. Unlike those drugs, it protects the stomach lining instead of irritating it (see Stomach and gut).

The same NRF2 theme runs through several other supplements on this site, including beets and Chinese skullcap.

Liver

In people with fatty liver, five trials with 358 participants found that black seed lowered the liver enzymes ALT and AST, lowered fasting blood sugar and CRP, and reduced the grade of fat in the liver on ultrasound.⁹

The liver is where the mechanisms overlap most. AMPK shifts the liver from making fat to burning it, and less oxidative stress means less of the damage that turns a fatty liver into an inflamed one. For liver scarring specifically, see Milk Thistle.

Stomach and gut

Black seed protects the stomach lining and reduces the inflammatory cells that gather in it. In people with chronic indigestion, a honey-based black seed oil preparation eased symptoms and lowered rates of H. pylori infection when added to standard acid-reducing treatment.¹⁰

Black seed also works against H. pylori, the bacterium behind most ulcers. In one trial, 2 g of ground seed a day with an acid blocker cleared the infection in 67% of patients, against 83% for standard triple antibiotics.¹¹ That makes it a useful add-on, not a replacement for antibiotics.

Viral illness

Clearing a virus depends on T cells, and black seed supports them (see Immune system). In a trial of 173 adults with mild COVID-19, half added one 500 mg capsule of black seed oil twice a day for 10 days to usual care. In that group 62% had recovered within two weeks, against 36% on usual care alone, and recovery came about a day and a half sooner.¹² The trial had no placebo, so some of that gap may be expectation.

In the lab, thymoquinone also interferes with how several viruses copy themselves. No human studies have tested it against colds or flu.

Candida, parasites and SIBO

In the lab, thymoquinone kills Candida yeast, breaks up the protective films it forms, and switches off the genes it uses to invade tissue.¹³ It also kills a wide range of bacteria, including some antibiotic-resistant strains.

That's the basis for using black seed against candida overgrowth and SIBO (small intestinal bacterial overgrowth). The same antimicrobial action is what works against H. pylori in the stomach, where it has been confirmed in people.

It also works against parasites. In mice infected with Schistosoma, a parasitic worm, black seed oil by mouth cut the number of worms and the eggs they laid, and visibly damaged the worms' outer surface.¹⁴

No human studies have tested black seed for candida, other fungal infections, SIBO or parasites.

Skin and hair

For skin, black seed works best applied directly. Across 14 trials with 732 people, black seed creams, gels and oils improved eczema, acne, psoriasis and vitiligo.¹⁵ In hand eczema, a black seed ointment worked as well as betamethasone, a prescription steroid cream, and better than a plain moisturizer.¹⁶

It works on skin for the same reasons it works elsewhere: it calms inflammation, kills the bacteria and yeasts that aggravate acne and dandruff, and helps skin cells make collagen and close wounds.

For hair, the reasoning is that a calmer, less inflamed scalp with less yeast is a better place for hair to grow. No human studies on hair growth have been published in the major medical journals.

Kidneys

In a trial of 60 people with kidney stones, half took ¼ tsp (500 mg) of black seed twice a day for 10 weeks. In that group, 44% passed their stones completely and another 52% saw them shrink. On placebo, 15% passed their stones.¹⁷

In people with kidney disease from diabetes, ½ tsp of black seed oil a day for 12 weeks lowered creatinine, urea and protein in the urine, and raised the kidneys' filtering rate.¹⁸ In animals, TQ protects kidney tissue from oxidative damage. Anyone with kidney disease should stick to these doses and tell their doctor; see Safety.

Brain

In 40 healthy older adults, ¼ tsp (500 mg) of black seed twice a day for nine weeks improved scores on tests of memory, attention and mental speed, compared with placebo.¹⁹ A companion trial in teenage boys found steadier mood and less anxiety after four weeks.

In animals, TQ protects brain cells in several ways. It raises BDNF, the brain's main growth factor. It slows the breakdown of acetylcholine, the memory neurotransmitter, which is how some Alzheimer's drugs work. It also reduces the build-up of amyloid and helps clear it.

Sleep

In 70 adults who woke unrefreshed, a concentrated black seed oil extract (200 mg a day, standardized to 5% thymoquinone) improved sleep within a week. Measured by wrist tracker and compared with placebo, they fell asleep about 35% faster, slept 19% longer, and woke less during the night.²⁰ The extract's manufacturer developed the product tested.

The likely reason is the same calming effect seen in the brain trials, where mood steadied and anxiety fell. In animals TQ raises serotonin and GABA, the brain's main calming signals.

Immune system and autoimmunity

Black seed seems to balance the immune system, strengthening a weak response and calming an overactive one.

• Healthy people: ½ tsp (1 g) of ground seed a day for four weeks raised total lymphocytes and helper T cells in young adults. Doubling the dose lost the effect, which is one reason not to take more than the usual amount.²¹
• Hashimoto's thyroiditis: eight weeks of ground seed lowered TSH and the anti-thyroid antibodies that drive the disease, and raised the active thyroid hormone T3.²²
• Rheumatoid arthritis: two 500 mg capsules of oil a day (about ¼ tsp) for eight weeks raised IL-10, the immune system's main calming signal, and lowered markers of oxidative stress.²³

Fertility and hormones

Sperm are easily damaged by oxidative stress, because their membranes are rich in fragile fats and they carry little antioxidant protection of their own. In 68 infertile men, ½ tsp (2.5 mL) of black seed oil twice a day for two months improved sperm count, movement and shape, and semen volume, compared with placebo.²⁴

In 103 teenage girls with polycystic ovary syndrome (PCOS), 1 g of black seed a day for 16 weeks made periods more regular and reduced ovarian volume, when compared with standard hormone treatment.²⁵ PCOS is driven largely by high insulin, so this fits the blood-sugar effects above.

Eyes and bones

The retina burns more oxygen for its size than almost any other tissue, which makes it prone to oxidative damage. In animal models of glaucoma, diabetic eye disease and retinal injury, thymoquinone protects the retina and optic nerve by lowering oxidative stress and inflammation and by keeping nerve cells alive.²⁶

No human studies have tested black seed for eye disease. Itchy, watery allergy eyes did improve in the hay-fever trial above.

Bone is constantly broken down and rebuilt, and inflammation tips that balance toward breakdown: TNF-α and IL-6 switch on the cells that dissolve bone. By lowering those signals, black seed should favor rebuilding. In animals it speeds the growth of bone-building cells and raises bone density. No human studies have measured bone density.

How to take it

• Oil: ½–1 tsp a day. The trials used ¼–½ tsp (1–2.5 g). It tastes sharp and peppery, so most people take it with honey, in a smoothie, or as capsules.
• Ground seed: ½–1 tsp (1–2 g) a day, stirred into food or a smoothie. Grind about a week's worth at a time and store it airtight and away from light, because the oils in the seed go stale once it's cracked.
• With fat: thymoquinone absorbs poorly on its own and needs fat to carry it. Take it with a meal.
• On skin: rub the oil directly on the area once or twice a day. Try a small patch first.
• How long: most trials ran 4–12 weeks before measuring a benefit.

Oil or ground seed?

Both work, and the trials above used both. Each has a trade-off.

• Oil is concentrated and easy to take, and it's the form to use on skin. Its weakness is consistency. Thymoquinone content in commercial oils ranges from about 0.07% to 1.9%, a 27-fold spread. Choose a cold-pressed oil in dark glass that states its thymoquinone percentage on the label. The oil is also 50–60% linoleic acid, though at a teaspoon a day that's only about 2.5 g (see Linoleic Acid).
• Ground seed avoids the potency lottery and brings the seed's fiber with it. It takes a little more effort, and it isn't suited to skin.

Safety

Medications: because black seed lowers blood sugar and blood pressure, it can add to the effect of drugs that do the same. It may also slow blood clotting, so stop it before surgery and take care with blood thinners. Pregnancy: food amounts are fine, but avoid supplement doses. Skin: the oil occasionally causes a rash where it's applied.