The environment is used as a broad umbrella term for all sources of allergens which may cause allergic hypersensitive reaction of the immune system of humans. Westernization of life leads to increased average consumption of food additives (natural and xenobiotics) – starting from over 5kg (10lbs) annually with a strong tendency to intensify. Modern technologies of food production often employ substances improving quality, texture, colour, taste, acidity or alkalinity. Haptens present in food or drugs, penetrating organism via gastrointestinal tract, may be responsible for symptoms not only in the gastrointestinal tract itself, but also in peripheral organs. Mechanisms of hapten action within human body are different – they include reactions when the immune system is involved (allergic hypersensitivity) and not involved (food intolerance also known as non-allergic hypersensitivity). Food intolerance is a more frequent phenomenon diagnosed in 20-50% of cases; food allergy affecting 6-8% children and 1-2% adults. Our work elucidates mechanisms of hypersensitivity responses to haptens, and characterizes major haptens applied as food additives.