I get an Itchy Eustachian Tube and what works for me is:
-plug nose & keep mouth closed and push air out - pop ears; and
-close mouth and make sure your throat is closed, then tilt head back and pour Nasal Saline Solution up your nose, shake head a bit, and bring head back down and blow your nose into a kleenex.
Keep cleaning your nasal passages out this way and you'll see that soon the itch will be gone. Whatever bacteria got lodged in there will be flushed out.
Some people, their Eustachian Tube won't drain properly and then bacteria can grow, causing the tube to become quite itchy. Keep it flushed out! Saline Solution disinfects.
Good Luck!!