I doubt its the blackseed oil (black cumin oil). I've used it for years and its actually helped calm my colon when having diarrhea. It's known to have anti-inflammatory properties and has been studied for various other things.
I hope you were taking cold-pressed black seed oil and not the one from Hemani which solvent processed with hexane and blended with a carrier oil. There are other good brands out there which are cold-pressed and have excellent quality.
See this article in Natural News: www.naturalnews.com/038644_black_cumin_oil_immune_system_NK_cells.html
Hope this helps!