I had gone through your medical history and understood your concerns. By carefully seeing your complaints, you were suffering with persistent cough (chronic cough). As there were no signs of fever, congestion, runny nose, you might be diagnosed as bronchitis. But the only reason that is taking us away from diagnosis of bronchitis is, in bronchitis there will be productive cough. Moreover your chest x-ray was also normal. Coming to further evaluation and diagnosis of your chronic dry cough, the cause might be cigarette smoking, environmental pollutants, allergic substances or asthma to little extent. So check all the above factors. As cough was associated with red rash, the probable diagnosis may be an allergic substance might have gone into your respiratory tract. Take care of the following things: 1. Use cough syrup 2. improve your immune system 3. reduce your exposure to allergic substance Follow the instructions carefully and act accordingly. Hoping a speedy recovery.