EBF Baby sick on formula

[LolaLollypop]

DS2 is 6 months old and EBF. I've recently tried a couple of bottles of formula when I've had invitations out for the evening. Initially I tried Aptamil (half expressed breast milk and half Aptamil). Poor DS was sick 5 times and DH had to ring me to come home. I was then recommended Hipp Organic by a friend. Just tried that again tonight as a tester and he's been sick again in bed, looks like more than once.
Has anyone had a similar experience? Could it be an allergy/intolerance? Something in the formula making him sick? I eat loads of dairy and he's never been sick before whilst having boob milk.

DD1 took a bottle of Aptamil no problem at 6 months so this is all new to me! Anyone else have a similar experience?

What happens if he just has expressed bm?

@Lockdownseperation he's fine. He can take the bottle no problem. I could just express I guess but would like the option of adding a bit of formula if needed.

This happened to my little boy who was EBF and I wanted to try introduce a bottle of formula. Turns out he had CMPA. He did have other symptoms from dairy in my milk but I put it down to other things such as colic, eczema, etc.

Because of Covid he hasn’t actually had the tests but I cut the dairy out of my system and the symptoms went.