The front of my tongue no longer tastes, and barely feels anything, after dental surgery (probably local anesthetic from a root canal). I can still taste in the back of my tongue, thankfully, but my sense of taste overall has definitely diminished. I feel sorry for your cousin.

I had gotten the local anesthetic several times without issue, it was just that one time that I got unlucky. Supposedly if the sense of taste doesn't come back after two years it's not likely to, so I guess this is my life now.