Reaction or Virus?

This morning Z woke up with an upset stomach, nausea and a headache. Three of my children had dental appointments and if you do not cancel with a 48 hour notice they will charge you $50 per child. So I loaded up the the kids, this was to include Z who still was not feeling well, and headed to their appointment. We had to pull over a couple of times so Zachary could throw up outside the vehicle. When we got there I took the two well children in and left Z in the van with a bucket. I explained to the receptionist that Z was really sick and was in the car if they were insistent on him keeping his appointment. I pretty much figured that they would gladly excuse the one throwing his guts up if I had him in the car. I was ready to bring in proof in needed, lol. They said that they would waive the fee for Z and would reschedule his appointment. I went back out to the car and waited while the others saw the dentist and only had to have a short talk with one of them because they were not cooperating. On the way back home and for the rest of the day Z dry heaved ... He could not keep anything down, not even water. I called our family doctor and asked if they could tell if Zachary had a virus or if he was having an allergic reaction. The person on the phone said I would have to bring him in for a diagnosis, so because I am the curious one I took him in. When we got there Z was crying out in pain because of the stomach cramping he was enduring ... when the doctor came in she examined him. Then I asked if she could let me know if this was an allergic reaction to the walnuts he had the night before or if it were a virus. She said she was leaning toward food allergy as Z did not have the common symptoms for the most recent virus going around, but could not verify that it was a food allergy for sure without doing allergy tests on him, in any case, she prescribed him with a shot of Phenergan which is used to relieve the symptoms of allergic reactions and help prevent and control nausea. The doctor also prescribed two other medications, but I do not remember what they were because I didn't even bother to pick them up. My thoughts were that if this one shot could not help Z then I would call Dr. Brown to see what his suggestions would be to help Z, besides that Z's appointment with Dr. Brown was the following day and we weren't going to miss it, because when we do it almost always haunts us later. When we got back home Z was still cramping pretty badly and the pain in his gut was up to a 9 on Z's pain scale. Later that afternoon I shot Dr. Brown a text letting him know that we thought Z might be reacting to the Walnuts from the smoothy he had the day before and I filled him in on Z's condition. Dr. Brown was glad that Z was throwing up, because that was his body's way of getting rid of or fighting off whatever it was. He also mentioned that sugar does lower the immune system so this could be related to all the sugar Z had over the Easter weekend. He suggested that Z sip on water with lemon in it so he would recover.