Very little is known about the safety of long-term use of black seed oil or when used in amounts higher than what’s normally found in food. However, there’s some evidence that applying black seed oil directly to the skin may cause an allergic skin rash (known as allergic contact dermatitis) in some individuals.
According to a report
, a component of black seed oil known as melanthin may be toxic in larger amounts.7
In a case report
, a woman developed fluid-filled skin blisters after applying Nigella sativa
oil to the skin. She also ingested the oil and the report’s authors state it is possible that the blisters were part of a systemic reaction (such as toxic epidermal necrolysis
Black seed oil may slow blood clotting and increase the risk of bleeding. If you have a bleeding disorder or are taking medication that affects blood clotting, you shouldn’t take black seed oil.
There’s some concern that taking too much black seed oil may harm your liver and kidneys. It’s possible that black seed oil may interact with many common medications, such as beta-blockers and (Coumadin) warfarin. Stop taking black seed oil at least two weeks before a scheduled surgery.
Pregnant women (or women trying to become pregnant) and breastfeeding women shouldn’t use black seed oil. Be sure to talk with your doctor if you’re considering taking black seed oil. You shouldn’t stop any of your medication without speaking with your doctor, or delay or avoid conventional treatment.