There is no definitive answer to this question. However, more than a few people with asthma relate that they have experienced increased mucus and or worsening of their asthma after drinking milk, sometimes with little delay. If this is just a small nuisance, you can probably continue to drink milk and eat ice cream. If it is more severe than that, you may want to cut back, but if you do, you should ingest more of other calcium containing foods or take a daily calcium supplement.
In some people dairy products, such as milk or ice cream, coat the mucus that is already present making it feel thicker and sticker. Whether it is the fat or another component of the dairy product is not known. Drinking plenty of water will help to thin the mucus so that it moves more easily.
My son is 15th months, is sick (vomiting, fever) and has so much mucous that he is constantly coughing and it sounds as though there is fluid on his lungs. Do I let him ride this out or is there a treatment for this so he can sleep and function more normally while this bug works through him?