Name a common allergen that must be avoided in certain dietary plans.

Gluten is a common allergen that must be avoided in certain dietary plans, particularly for individuals with celiac disease or gluten sensitivity. In these conditions, the ingestion of gluten, which is a protein found in wheat, barley, and rye, triggers an immune response that damages the small intestine and can lead to a range of gastrointestinal and non-gastrointestinal symptoms. This is why many dietary recommendations for people suffering from these conditions emphasize a strict gluten-free diet to prevent adverse health effects.

In contrast, while peanuts, lactose, and soy are also associated with allergies and intolerances, they are specific to different conditions. Peanuts can cause severe allergic reactions in susceptible individuals, lactose can lead to digestive discomfort in those with lactose intolerance, and soy is another allergen that can provoke reactions, particularly in children. However, the need to completely avoid gluten is uniquely critical for individuals diagnosed with celiac disease, which distinguishes it in dietary management discussions.