Talk to General Physician on Persistent Dry Cough Since 3 Months

Muje Persistent dry cough horhi h since 3 months. All test IgE, CXR even HRCT chest normal. No any history of TB, asthma, allergy, pets and post nasal drip etc. take all treatment include nebulizer, steam inhalation, syrups, myteka, anti allergy, PPI, even used dry powder inhaler etc but ksi se bhi koi farq nh para cough wesi hi horhi h like before treatment. Please tell me the best possible solution and further investigations. Note spirometry is not done due to ongoing cough that can affect its reliability. Thanks