As a parent, I completely understand your desire for answers but also really think you have to assess what information you will gain and what good it will do you and him. If he never chokes, never clears his throat, his asthma is well controlled on not too much medicine, what treatment option would you take if offered to you? (I hope he's still taking acid reflux meds if he needs them as acid can trigger the "tic.")
It sounds as if he's doing remarkably, wonderfully well but it's easy to see how traumatizing it must have been for you when he was little.
Allergies can cause drainage from the sinuses and that can drain down into the throat and cause irritation of the area around the larynx and also into the airway and cause spasm. So I kind of disagree with the doc who said no and if he were still having the tic, I'd have him take something like Mucinex (guaifenesin/Robitussin) to see if thinning any mucus helped. Also, I have all my patients with asthma wash their noses with neti pots or NeilMed bottle buffered salt water
to make sure mucus doesn't accumulate.
One way to think about could it be allergies is to map out when it occurs--or even where. Every spring when things start to bloom? When a visit to a farm or family with a cat? Stuff like that.
Many boys of 13 stay the same weight but grow taller as hormones are coming and they are pushed to grow. They don't put on weight until they stop growing, hair starts sprouting and voice gets deeper. Think about all the skinny, skinny young male teens who wish they could put on muscle and take all kind of OTC protein and carb drinks to try and bulk up--but can't. To us women, lucky time of life to eat whatever you want and not gain. As long as he's not losing and the docs say he's healthy, just feed him all he'll eat and wait.
I was confused with the EGD as that stands for esophago-gastro-duodenoscopy: looking into the esophagus, stomach and duodenum (first part of the small bowel.)
What you're contemplating is low risk but nothing's no risk and what you, your son, and his father need to figure out is what will be gained?
Do you have any further questions?