I'm actually curious about this too - I've had pretty great success with zinc lozenges, but was off-put by this. Although the study is for some very specific intranasal products from a specific brand, I think.

edit: Link to original study: http://archotol.jamanetwork.com/article.aspx?articleid=49648...

It talks about "homeopathic zinc gluconate gel" and some patients reported a burning sensation while applying it.