Can multivitamin cause headache? had headache days in a row while taking multi. stopped taking it and no headache; sinus/heat possible causes too?

Uncommon but yes: This is uncommon but possible. One can't be allergic to vitamins themselves but many supps have artificial colors/fillers, binders & allergens like soy that could trigger headaches. It could be a co-incidence.Try them again; if you get a headache every time then try a different brand without unnecessary additives. See http://www.Multivitaminguide.Org/ and yes, could be from sinuses/heat/dehydration.