Can you tell me what could be causing these whelps? They have a tiny blister in the center, seem to always recurr on my arms, chest, and back. They itch and are painful to scratch. Within three weeks after I complete a prescription of ranitidine/allegra, the whelps return. I went to the dr. 5 times last year. Creams don't help. This started in May last year. Would love to know how this works and what is causing this recurrence.