Diseases resulting from food hypersensitivity ("food allergy"). Drug-nutrient interactions
This topic covers the diseases that result from supersensitivity to food: true food allergy, which involves an allergic or immune response, and non-allergic food hypersensitivity, which arises from metabolic defects, enzyme deficiencies or hyper-reactivity to substances. It also covers how drugs and nutrients influence one another.
Food hypersensitivity: definitions and frequency
- Adverse reactions to food are called food hypersensitivity (the common term is "food allergy"). The term food allergy is used when an allergic or immune response is involved.
- About 2% of the world population have food hypersensitivity, and about 1% have real food allergy.
- Allergenic foods: milk, eggs, soy, peanut, fish. Other common ones are tree nuts, wheat and shellfish.
- Non-allergic hypersensitivity is due to a metabolic defect, enzyme deficiency (for example lactose intolerance) or hyper-reactivity to substances.
Mechanism and clinical picture of food allergy
- The immune system treats a harmless food protein as a threat. In the immediate (IgE-mediated) type, sensitisation produces specific IgE bound to mast cells; on re-exposure the allergen cross-links IgE and histamine and other mediators are released within minutes to two hours.
- Skin: urticaria, angioedema, atopic eczema. Gastrointestinal: vomiting, abdominal pain, diarrhoea, oral itching. Respiratory: rhinitis, wheeze, asthma. General: anaphylaxis with hypotension and airway swelling, which is an emergency treated with adrenaline.
- Allergens are usually heat- and digestion-stable proteins; cross-reactivity occurs, for example between related foods and pollens.
- Children are affected more often (milk, egg), and many outgrow milk and egg allergy; peanut, nut and fish allergy tend to persist.