I'm sorry to hear this. Black Seed/Black Seed oil are known as to help seasonal allergy sufferers, but Black Seed does lower blood pressure, which is why caution is advised. I'm not exactly sure about food allergies but black seed does build up one's immune system.
If your pressure is dropping too low and you're becoming anemic, then please STOP using it! Were you anemic prior to usage? Black Seed dilates the arteries and thins the blood, so someone with bleeding issues should avoid this. Dosage may be an issue here, or it may be that you are someone who has a low tolerance to the black seed oil.
In any case, as with any regimen, if you are having an adverse reaction, discontinue using it.