My brother went to a great Respiratory Dr after many treatments that never worked and he suffered until he started getting injections in tummy every 2 weeks for this allergic reaction. Non stop cough my poor brother & he’s okay now! See a Respiratory Dr & ask about allergy or vagus nerve but mention injection on tummy every week then every / weeks etc. A nurse comes to hive it but anyone can be taught to do it themselves. He’s a new man. God love him. Keep searching allergies bad immune system cough so bad. It’s to build immune system. Immunotherapy not sure but Respiratory Dr figured it out without allergy testing.. miracles happen. Not sure if that’s your issue but keep searching.