There are several common types of congestions, nasal and throat being the most common. Nasal congestion is characterised by an amount of stuffiness or swelling of the nose, sometimes accompanied by a runny nose. Throat congestion is most commonly coughing or pain or difficulty swallowing. People experience these symptoms after eating, and they can have a number of causes, some of them connected to food, others not.
A food allergy is one of the leading causes of congestion after you eat. A telltale sign of a food allergy occurs when you experience congestion an hour or sooner after eating. You could be allergic to any number of foods, so keep a food diary. Write down what you ate, what time you ate it, how you felt while eating it and how you felt in half-hour intervals after eating it.
Chronic Throat Infection
According to Dr. Douglas Hoffman of iVillage, in the throat, "Commonly infected structures include the tonsils, lingual tonsils and adenoids. Each structure is an example of lymphoid tissue, collections of cells that are supposed to fight infection. As front-line troops, these structures can become chronically inflamed as a result of viral or bacterial infections." It is possible that when you eat you're just irritating an infection that you already have, and thus making it feel more swollen and inflamed. Thus, what you could have is an infection masquerading as a food allergy.
What might appear to be congestion caused from eating a certain food could actually be a result of the environment where you consumed the food. Dusty environments with lots of pollen or mould around could easily produce types of congestion. It is possible that the food you're consuming is fine, rather the environment that you're in is triggering an allergic reaction.