you need to eliminate all mucous forming foods. the main groups are your dairy products (expect yogurt) and foods that are high in sugar. Try switching to rice or soy milk. Natural plain yogurt can be given, this will help to thicken the mucous so that it can be more easily eliminated from the body. Cold and refrigerated drinks should be discouraged. Give him warm water during the day, this will also assist will elimination of mucous through the bowels.