
I am so sorry that you had such a trauma but at least you were close to the hospital and knew meds to give guickly. There are 2 possibilities here. Tomatos are cross reactive to latex sensitivity and the shrimp are just like giving someone iodine to drink. If your son has no reaction to blowing up a balloon then it is a really good bet that it was the shellfish. Was this the first time he had eaten this item? Has he ever had any shellfish?

Doesn't matter some of us just one day fall off the cliff into allergies. Find a good allergist. If he wants to start with a test called True test don't. Or just have him blow up a balloon if nothing happens shellfish/iodine goes on all his medical records, also get med-alert bracelet listing iodine as anaphylatic allergy. Hope things go better.