Hi and Welcome to the Forum!

Some people with mast cell disorders have hives and Hashimoto's thyroiditis (I have the latter.)

There are some blood and urine tests that are usually done in a work-up for MCAD.  The testing is listed on this forum, as well as information on being worked up.  Read all you can about MC diseases so you can be well-informed when you meet with the hematologist.  The BMB will show if you have systemic mastocytosis or other hematological issues, but even if it's negative, you still can have mast cell activation problems.

Do you know what triggers your hives and swelling?  Foods, for example, may not be true allergens for you, but they can still be "triggers" and cause symptoms.

If you want to post your current meds, people will comment.  Most allergists put MC patients on too little doses of antihistamines to be effective.

Let us know how you're appointment goes, if you want to share that.  Everyone on here cares!