Gastrointestinal tract is a lymphoid organ, and the lymphoid tissue within it is referred to as the gut-associated lymphoid tissue or GALT. Gastrointestinal allergy is an immediate hypersensitivity reaction of the digestive system after the ingestion of certain foods or drugs. GI allergy varies from food allergy, which can affect other organ systems. Distinctive symptoms constitute itching and swelling of the mouth and oral passages, nausea, vomiting, diarrhoea, severe abdominal pain, and in severe cases, anaphylactic shock. Gastrointestinal food allergy also urges a challenge to the clinician because of its mutable symptomatology and lack of accurate diagnostic tests.