Dry cough. It is always better to determine the cause of a symptom rather than simple treating the symptom itself. Seek a doctors advise and undergo an examination for any cough lasting more than 2 weeks.
Diagnose. First you need a diagnosis for the cough. Possibilities for a chronic cough lasting more than 3 weeks includd bronchospasm, post-nasal drip, gerd or a combination of 2 or more of these. Diagnosis will often require testing. If you are smoking, you need to quit and your doctor can help with this too. Good luck!