One of the active ingredients in some mouthwashes is known to cause taste loss: https://www.reddit.com/r/Dentistry/comments/21vddm/i_lost_my...

I discovered this after starting to use Crest Gum Care mouthwash and it was pretty annoying.

Luckily the loss of taste was not permanent and returned a few days after stopping use.

Yes, ceedan says that somewhere in the world there is a toothpaste that if you use it, it will burn up your tongue and you will loose your sense of taste... yet doesn't provide the name of the toothpaste. WHY?

I actually read it not as:

Toothpaste burned my tongue, therefore I lost my sense of taste.

but as:

I lost my sense of taste, therefore toothpaste burned my tongue.

which might not make so much sense as an affect of the losing taste, but does explain why they don't name the toothpaste.

Chemical burn. Probably less common nowadays. My experience was in 2007. The name for this seems to be "burning mouth syndrome"