What can I do about my allergies at night?

Can a toddler's allergies make him throw up at night, sporadically?

• My son is 27 months old. 3 weeks ago we went to the pedi for his yearly physical and he got a flu shot and one booster for his immunizations. That night, he got violently sick, threw up several times and was shaking due to freaking out. After talking to the pedi on the phone, it was dismissed as a slight reaction to the flu shot, and the next day he was fine and hasn't had any issues since. Tonight, however, I heard him hacking/coughing and when we checked on him, found that he had thrown up all over his bed again. We had something we have all the time for dinner(keilbasa and mac and cheese) and no one else is sick from it, so it's not food poisoning. We didn't go anywhere today, and there was no stress for him today, but the pollen count is extrememly high with the super warm spring we've been having, and he's been sounding a bit mucusy, like he has allergies. Now, he seems to take after my brother physically, and my brother suffers from post nasal drip to the point where he wouldn't eat a lot because he was always full. Obviously, I'm going to call the pedi in the morning but has anyone else ever had this happen to their child? What was the cause?

• Answer:

  If he was coughing due to the mucus/allergies, he could have thrown up from that. It's called post-tussive emesis. Or he could have picked up a stomach bug - it happens all the time.