What Caused My Seizure On Smelling Blood?

I have never had a problem with blood untill the other night when i passed out after smelling some from a fresh tattoo. It happened several times and each time i did, i began to have a fit/seizure untill i came around. Medic's turned up and checked me over, they didn't find anything wrong so i decided to stay at home. I understand that i possibly passed out due to the blood but i don't understand the fit's, iv'e never had one before. Any help would put my mind at ease.