Something strange about Antibiotics

Greetings

So I've noticed this strange thing about my son and antibiotics. Now he is allergic to many of them. He can only take a few. The first time he took amoxicillin he wound up in the emergency room looking like a ripe tomato. 

However, whenever he gets a sinus infection or any other infection (which is often) because we can't keep his hands out of his mouth he gets placed on antibiotics of course.

Well.. while on antibiotics his cognitive abilities INCREASE. His communication and motor planning simply improve.

It's the strangest thing ever. Leads me to believe that gut microbacteria play a greater role in things.