I am wonder if I had an allergic reaction to some potassium
metabisulphite. This is the first time I used it, and it was
technically for homebrewing, but I figured the vintners would know more
about it.

I had read to use sulphites to santize beer caps so it doesn't react to
the caps in a water solution like other sanitizers. I've had caps rust
in a water/sanitizer solution, so I was motivated to try . I put about a
teaspoon in a small bowl of tap water, and immediately my nostrils and
throat felt like they were burning up.

The reaction wasn't severe, but hardly pleasant. The next day, I have a
slightly itchy throat. Could that be from the sulphites? It doesn't
seem like a regular asthma reaction, and I don't have any major allergies.