It sounds to me like you had a whole series of triggers for the panic/anxiety attack starting with the allergy reaction. These types of situations are often handled quite easily with EFT (emotional freedom techniques)by tapping on accupressure meridians while focusing on the issues that cause the anxiety/panic/allergy. If you would like to learn it you can go to emofree.com and download the free 80 page tutorial and try it. It takes some patience to get a handle on using it at first but if you are diligent you should see results.
If you want faster results I teach EFT over the phone and most folks are feeling better within the first ten minutes. Give me a call if you need help. I only charge a reasonable fee if you get relief from the anxiety.