No Barley. As long as you have no other known allergies, you may eat anything you like just so long as it does not contain barley.
Grain allergy. Allergy to any food, in this case barley will cause symptoms of oral itching, lip or tongue swelling, hives, breathing difficulty and/or throat closure etc. Food allergy is diagnosed with clinical history followed by skin or blood test and that information helps establish the diagnosis and severity of the allergy.
I have a barley allergy confirmed with a blood test. Was tested for wheat, rye. Is it common for barley allergy to "standalone" or similar substances?
Barley allergy. Yes barley allergy alone is actually very common. I usually see 6-7 people a year with this allergy. Usually it causes itching alone (which can lead to eczema), recurrent urticaria (hives) and/or intestinal cramping with diarrhea. The hard part with avoidance is that many brands of flour are a wheat/ barley mix. So this calls for a lot of label reading and avoidance of things made with flour.