Oregano oil we don't have in fact, but certainly we have been using colloidal silver. I considered something along the lines of the food elimination process you described but it seems to me like it will still be difficult to identify when we have hit the target. He can go for weeks without feeling pain. So, unless there is an immediate difference to the way he speaks and breathes, how will we know we have identified the cause of the allergy without waiting months?
Anyway, let's see for that one. Looking forward to trying out some of the ideas presented here. And will put oregano oil on the shopping list! Thanks for that one.