Up to 20% of the population perceive themselves as suffering from food allergy
but only 1-2% of adults have genuine food
allergies. The most common culprits are peanuts, milk, eggs, soya and shellfish. You will have to observe which food, on consumption is causing this problem.
It could be an allergic reaction, more so if the symptoms have occurred with the consumption of the same food. Maintain a food dairy and note down and monitor your symptoms. This may help to narrow down the search.