According to Tibetan medicine, diets that are fatty, oily, fried, salty, and animal products like milk and cheese are not recommended. Also foods that are sour like lime and lemon, stale and frozen food and cold drinks should be avoided as these accumulate more mucus in the body. Try to eat more warm and cooked food and drink boiled warm water. This is considered very beneficial to bring the phlegm out of your system. Avoid sitting on wet damp places, avoid smoky areas, and dust, always try to keep your body warm and always remember to get the mucus out whenever you can. I also would suggest you do some breathing exercises early in the morning when the environment is not so polluted. Going out for a walk in the woods or among trees, also in the morning or evening is very beneficial.