@hottamalee, my little one didn't seem to have an issue. Every baby is different. If he has an adverse reaction it could just be the formula brand as well. Certain formulas agreed better with my LO than others.
I just did one oz of formula to start off so its easy on her belly and did 3 0z of breastmilk and mixed them :) after a few days of mixing i uped the formula to 2oz of formula and 2 oz breast milk just so its not so harsh! its nerve wracking at first