A food-intolerance reaction resulting from the pharmacological effect of a food component. A well-known example is caffeine, a methylxanthine derivative present in coffee. Its biological action includes stimulation of the heart muscle, the central nervous system, and the production of gastrin. Symptoms associated with a high coffee intake are restlessness, tremors, weight loss, palpitations, and alterations in mood. Other biologically active substances are histamine, tyramine, phenylethylamine, and histamine releasers.