An oligoallergenic diet is a highly restricted eating plan used diagnostically to identify foods triggering symptoms such as eczema, gut complaints, or behavioural changes. The patient eats only a small number of foods considered least likely to provoke reactions, classically lamb, rice, and pears in older protocols, for a period of weeks while symptoms are monitored. If improvement occurs, foods are reintroduced one at a time to pinpoint culprits. The approach demands dietetic supervision: such narrow diets risk deficiencies in protein, calcium, iron, and B vitamins, and prolonged unsupervised restriction can cause malnutrition, especially in children. Modern allergy practice favours targeted testing and supervised food challenges over broad empirical elimination, but oligoallergenic diets retain a role when multiple sensitivities are suspected and standard tests are unrevealing.