Black seed oil (Nigella sativa) is widely used as a natural remedy and in beauty products, but scientific research doesn’t always back up some of its claims. Black seed oil can cause allergic rashes and interact with certain medications, so it’s important to use only a high-quality product that is 100 percent pure and therapeutic-grade, says Cleveland Clinic’s Chair of Wellness & Preventive Medicine Robert Saper, MD.

The oils in the seeds of this ancient plant are thought to have powerful antioxidant, antibacterial and anti-inflammatory properties. They’re available in capsule and liquid form, as well as in lotions, makeup and other beauty products. You can buy the oil in health food stores or online. It may also be available at some pharmacies and natural-medicine stores.

Some studies suggest black seed oil benefits include reducing blood pressure, helping with infertility and improving skin rashes, allergies and other conditions. Thymoquinone, a compound in black seed oil, has been shown to boost the number and motility of sperm cells. A small clinical trial published in Phytotherapy Research: PTR found that men with abnormal sperm count and low semen volume who took 2.5 milliliters of the oil twice daily for two months showed improvements.

However, more clinical trials are needed to verify the results of this study. Other studies show that black seed oil has antidiabetic properties and can improve a person’s blood sugar levels. One randomized controlled trial found that people who took black seed oil experienced a drop in systolic and diastolic blood pressure.