Your mother might have told you to stay away from milk when you're sick with or recovering from a cold, but according to medical studies done in Switzerland and Australia, dairy products don't increase congestion. It's important to drink fluids during infection, and it's OK to drink milk, says Dr. Robert H. Shmerling of Beth Israel Deaconess Medical Center on the Aetna InteliHealth website. If you do feel stuffy after drinking milk, you could be allergic to it.
People with milk allergies should avoid milk. Those individuals are allergic to casein, the protein in cow's milk and milk-based dairy products, and are more often diagnosed as infants and children; however, it is possible to develop a milk allergy as an adult. A stuffy or runny nose can be one of the symptoms of a milk allergy, but there are other, more common indications of this, including diarrhea, vomiting, skin rashes, bronchitis and respiratory problems, according to ENT UK. Milk allergies can be diagnosed by skin tests or blood tests.