May be he had mononucleosis. Mono is usually linked to the Epstein-Barr virus (EBV), but can also be caused by other organisms such as cytomegalovirus (CMV). I don't think Anti-Thyroglobulin antibodies are related. Did he had any kind of symptoms? did he test for liver enzymes? Yes allergy can cause high eosinophils.
His only symptom was his sinuses always being what his Ped. referred to as "sounding swollen." He doesn't have a runny nose he sounds like he is impacted and alwyas has a dark bruise looking strip across the bridge of his nose. He also has a history of vocal cord dysfunction (cords don't spread apart when he draws in a breath) This causes him to sound like he is wheezing on inspiration. Asthma meds have no effect.