Background: Persistent fever worried many patients all over the world, however, none clear etiology was found.
Methods: Four outpatients with persistent fever were selected and tested by vitro test of skin prick tests and vivo test of serum specific IgE (sIgE) tests was treated with omitted from their allergic food and received specific immunotherapy for a period of time.
Results: Two cases were well relieved from the fever and nasal obstruction just by omitting from the allergy food like beef and egg respectively. Two cases were also remitted greatly from PF by pollen specific immunotherapy for almost six months.
Conclusions: Persistent fever could be caused by food or pollen allergy disease. However, not treat it anymore with a cold medicine like paracetamol. Thus, allergic factors we suggested should be considered when dealing with persistent fever clinically.