I had a barium swallow quite recently and I was terrified before I got it! I have a phobia of food induced anaphylaxis, and I was convinced I would have an allergic reaction to the barium contrast, or that it would become hardened and impacted in my GI tract. I know exactly how you feel, and it can be very scary. But I must tell you that I was actually pleasantly surprised! My radiologist was wonderful! Very kind and patient! I immediately informed him of my fears, and he and his assistant were extremely patient and encouraging. They told me no question was a stupid question, and they talked me through the entire procedure.
I can tell you this. The barium contrast is considered hypoallergenic, and an allergic reaction to the liquid is extremely rare, almost unheard of. It tastes kind of like a berry milkshake, but is fairly easy to swallow and not bad at all. The whole procedure only took about 10 minutes, so it's super quick. You get your results within 24 hours, so you don't have to wait forever to find out about your tests. And, as long as you drink plenty of water and eat a high fiber diet for the next 3 days after your procedure, there's virtually no risk of impaction / obstruction in your GI tract. You will just have light colored stools for a few days, you pass the barium, and it's done. Super easy! Nothing at all to be worried about! I promise! :)