Welcome to the forum, Anna.
How do you know you are allergic, or is it sensitive, to sulfites? There isn't any approved test. Have you seen an allergist? Do you keep a food journal/diary? I had to keep a journal for months, on my allergist's directions.
I don't know if blood pressure is related to sulfites. Mine is a little high, but I think it's familial. I get stomach upset/gastric reflux and sometimes tachycardia when I go over my tolerance limit for sulfites. But I think most people get migraines as the main symptom. But these are sensitivity reactions, not allergic.
What foods make your throat itchy? It's possible to have more than one intolerance at the same time. I had to look up my list of foods and the words "food allergy" to find what my problem was. I'm just saying make sure it's only sulfites. A lot of foods overlap into different categories.
Mostly, there are no set recipes for sulfite avoidance. It depends on your level of tolerance. You can calculate that from the information in Rick Williams' free online book No Sulfites. www.learningtarget.com/nosulfites/
The main thing in recipes is to avoid processed foods. Cook from scratch. Don't use corn starch for thickening, or corn syrup for anything. Look up the ingredients in any recipe in any cookbook and just don't make food with high levels of sulfite - depending on your own level of intolerance, which you calculated from Rick's formulae. My level isn't horrible at 2000 micrograms a day. I can have one soda OR eat one small slice of plain cheese pizza, if I don't consume other high sulfite foods the same day.
Ask your allergist about
the amount of Clairitin you take. I don't know how much "a lot" is, and I'm not a doctor either. Maybe your allergist can suggest something else to take. But mainly avoid your allergy triggers!