My Wife Has Developed Canker Sores On Her Tongue, Which

My wife has developed canker sores on her tongue, which has given her the sensation that it is swelling. There are many which surround her tongue and seem to be getting worse. She Also has a swollen gland in her neck. She feels like she is having an allergic reaction to something she ate or was exposed to. Recently she went into the doctor with some shooting pain in her head. They felt she had the beginnings of shingles. She took the medicine (steroid) for a while and then stopped when her symptoms got better. The only think she has been eating differently are tangerines. I gave her some benedryl and she is sleeping. Thoughts?