My friend AMYRN referred me to this board regarding another post, and I stumbled upon this one that she posted about my husband! How sweet! What a thoughtful person she is! I didn't even know she had posted it. And she's not even someone I've ever met! We met online, and she was kind enough to post this to try to help me out when I was literally freaking out!
As an update, my husband had an MRI. The day he had it, the numbness went away! After we paid $600 cash for the procedure! So the MRI cured him! Ha ha!
Anyway, the person who mentioned the allergy.........that might be the closest. This is going to sound weird. It always happened after he drank his morning coffee from 7-11. It would be fine in the morning, he'd drink the coffee, and wham the tongue went numb. And was numb all day until late at night or the next AM. He kept telling me maybe it was the coffee, but I thought he was nuts. He didn't go to 7-11 the day of the MRI, and hasn't been back, and the tongue hasn't been numb since. Now he still drinks coffee, just not from 7-11. Go figure.
The MRI was negative.