A lot of vitamins have unlisted fillers. You should also try to get gluten-free and dairy-free vitamins. You could have an unknown allergy to a vitamin or mineral, too. I stopped taking a multivitamin for 2 years, but I started taking one again without any fillers. Since my mom gets a rash when she takes B12, I try not to take much of it. I have never been deficient in B12, though.