A cough with phlegm for 2 years, especially if you smoke daily, is often due to chronic bronchitis or smoking-related lung damage. The most important step is to stop smoking, as this is the main cause and continuing will worsen the problem. You should see a chest physician for tests like a chest X-ray and breathing tests. Treatment may include inhalers, medicines to thin mucus, and lifestyle changes. Early care can prevent long-term lung damage.

If you have a long-term cough from smoking and drinking cold drinks, stay hydrated, use a humidifier, avoid cold or dusty places, and try steam inhalation. It is also essential to consult a doctor to rule out infections, asthma, or acid reflux as causes.

A cough lasting 4-6 months often comes from untreated allergies, acid reflux, asthma, or post-nasal drip, not infection. If it keeps returning, you may need a chest X-ray, spirometry, or reflux treatment to find the exact cause and treat it properly.