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The body’s response to a foreign protein (allergen). An allergen is a substance that, in an allergic person, provokes an immune response. The allergen is ‘attacked’ by the antibody immunoglobulin E (IgE), which also triggers blood cells to release histamine and other chemicals that together cause the symptoms of an allergic reaction, such as sneezing, runny nose, itchy eyes, rash, shortness of breath, wheezing. Common allergens are grass and tree pollen, house dust mite faeces, animal dander, wasp and bee venom, chemicals, medicines, and foods (milk, eggs, less commonly nuts and fruit). See also Anaphylaxis, Food allergy/intolerance 

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