Hi Elsah, Just wanted to say that you might want to consider whatever the splenda was in as a possible culprit for your sons hives. If it was just pop, then it's even possible it could be the citric acid. There's so many possibilities that you should check every avenue. Take it from someone who carrys 2 epipens everywhere she goes, allergies can be deceiving. I've been fooled on what it was when eating foods with different grains only to find out it's not the grains at all that I'm allergic to but what's not supposed to be in them in the first place (grain mites). They have a similar make up to dust mites and cause allergic reactions to people who are dust mite allergic when ingested. Believe me, it's a step of faith to eat grains when you never know if you're going to react. Just my 2 cents worth and Good luck with him, Annie