Luckily the only experience I have of issue here is with a chronic geographic tongue which basically if you were to bite your tongue and then drink lemon juice is what it is like for me 50-75% of the time. I can control the genetic disease with a high zinc content (usually from a liquid supplement). But on several occasions in the past it has been that bad I have not been able to eat or drink for a couple of days at a time and on one of those occasions, the UK was in the middle of a heat wave and I lived in the one of the hottest spots. I ended up needing IV fluids and A&E.... It wasn't a great solution but I didn't want to be hospitalised... Luckily after the 2nd visit the next day for fluids, one of the dr's had the sense to contact Guy's Dental hospital in London and it was suggested that they put lidocaine gel directly onto my tongue (after checking it did not set off my asthma too badly) and it numbed my tongue and mouth enough for me to be able to swallow a few small mouthfuls of water. After that I was fine, it wasn't ideal because I could only do it when it came to drinking, and you have to be very careful with the dose, but it did work.