Side Effects of Black Seed

More commonly referred to as black seed, black cumin or fennel flower, Nigella sativa is a flowering plant used in herbal or folk medicine. It's said to have a number of beneficial properties for your health. It can lessen inflammation, relieve pain, fight infections and reduce fevers. Black seed is also thought to prevent and inhibit the development and metastasis of neoplastic cells associated with cancer. However, scientific evidence is limited on its efficacy and safety, and black seed may cause side effects in some people. You should always talk to your doctor before taking this or any other herbal supplement to treat a medical condition.

A close-up of black cumin seeds. (Image: bdspn/iStock/Getty Images)

Contact Dermatitis

One potential side effect of black seed is contact dermatitis. Contact dermatitis as an adverse reaction to either an allergen or irritant. Simply touching black seed may cause a red rash along the skin. This rash is often accompanied by an itching sensation. It may also result in blistering, pain or tenderness isolated to the exposure site.


The Memorial Sloan-Kettering Cancer Center cautions that black seed can lower blood pressure to the point of hypotension, especially if you're currently taking a diuretic or antihypertensive medication. The drop in blood pressure impedes the transport of oxygen to the brain, heart and other organs. This can result in fatigue, nausea, blurred vision, shallow breathing, dizziness, lightheadedness and loss of consciousness. If blood pressure dips too low, it may be life-threatening.


Women who are pregnant shouldn't take black seed for any purpose, according to the Memorial Sloan-Kettering Cancer Center. This is largely due to the fact that the herb may affect the smooth muscle contractions of the uterus. Further assessment is necessary to determine exactly how this can affect pregnancy, so it's best to avoid this substance when expecting a child.

Adverse Interactions

Black seed is also known to adversely interact with both chemotherapy medications and radiation, according to the Memorial Sloan-Kettering Cancer Center. Since it may act like an antioxidant in the body, this herbal supplement can decrease the efficacy of standard cancer treatments.

Other Allergic Reactions

As with almost any herbal supplement, there's the potential for an allergic reaction from ingestion. Unlike contact dermatitis, this allergic reaction isn't isolated to the skin. It may cause swelling of the lips, tongue, throat or face as well as difficulty breathing, a tingling sensation in the mouth, hives, dizziness, nausea, vomiting, diarrhea and abdominal cramping.

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