Hi thanks for asking question. Let me know you do you have acid reflux disease???? Because acid reflux can lead to cough for prolong duration. For that omeprazole can be taken.While sleeping keep head below pillow . so reflux will be less.Avoid smoking. Avoid excess spicy food. During day time drink more and more water. Take fatty and fried food to a minimum for few days. I am giving above advise because although no fever previous attack of pharyngitis or sore throat can lead to long time dry cough. Tulsi and ginger useful herbal remedy. Onion will be good in soothing respiratory tract. If still symptoms increasing then chest x ray done for further work up. Wish you good health. Dr.parth