Reaction to formula.

So little one had a reaction when I tried him on HIPP organic formula about 2 mo the ago. He got hives and was fussy. It was about 2-3oz of straight formula.

Now we do 1/2 breast milk and 1/2 formula (similac organic ready made). He’s doing great but I have so much HIPP that I already had ordered. I’m wondering if that initial reaction was just it being 100% formula?

Do you think I should try it again? But maybe 1/2 HIPP and 1/2 breastmilk? He’s also a bit older, around 3-4 months.

Thanks!