Not asking for medical advice, just wanting to know others’ experiences.

My son is almost 10 months old, and he had a few bites (probably a little over an ounce) of yogurt yesterday and loved it. No reaction thankfully because that’s what I was worried about. So today, he had some more of the exact same kind of yogurt as the day before and loved it again, but this time, about 30 minutes later, he projectile vomited 3 times within a minute. 😱 He has never done that before. I would think it is a reaction to dairy, but if that’s the case, wouldn’t he have also reacted yesterday? He has no other symptoms and seems to be feeling fine, acting very happy in fact. Thoughts?