My father is a heart patient who had 4 bypasses september last year. last week he developed dry cough which is so irritable.

See doctor...: There are many possible causes for a cough. If it is of recent onset, it could be due to acute bronchitis, post-nasal drip, etc. A more chronic cough could be due to bronchospasm, GERD, post-nasal drip, etc. In this case, heart failure would be a concern as well especially if he is also complaining of shortness of breath, leg swelling, coughing pink sputum, etc. Take him to a doc for diagnosis.