A group of chronic disorders marked by persistent inflammation of the digestive tract, chiefly Crohn’s disease and ulcerative colitis. Crohn’s disease can affect any part of the gut and penetrates deeply through the bowel wall, while ulcerative colitis is confined to the colon’s lining. Both cause abdominal pain, diarrhoea, bleeding, weight loss, and fatigue, with unpredictable flares and remissions. Treatment combines anti-inflammatory and immune-modulating drugs with nutritional support: correcting deficiencies of iron, vitamin D, and B12, and adjusting fibre during flares. The abbreviation IBD is standard in clinical practice and research.