A cough with normal blood IgE may suggest that the cough is caused by non-allergic factors. There are many causes of cough, such as external stimuli, respiratory infectious diseases, allergic diseases, digestive diseases, etc. IgE is a kind of secretory immunoglobulin, which is mainly used to diagnose allergic diseases. Cough with elevated IgE is mainly seen in allergic cough or cough variant asthma caused by exposure to allergens such as dust and pollen. The most common respiratory tract infections cause coughs that are accompanied by fever, sore throat, and runny nose, but their IgE results are mostly normal. Coughs caused by digestive diseases such as gastroesophageal reflux disease (GERD) also have normal IgE results. A routine blood IgE test for cough can be used to rule out allergic coughs so that the cause of the cough can be further investigated.