What is an allergy?

When a susceptible person encounters an allergen, their immune system mistakenly identifies it as a threat and produces antibodies called immunoglobulin E (IgE). On the next exposure, the allergen binds to IgE on mast cells, causing them to release histamine and other chemicals. Histamine causes inflammation, itching, sneezing, watery eyes or, in severe cases, anaphylaxis, a life-threatening whole-body reaction. Common allergens include pollen, dust mites, mould, pet dander, peanuts, shellfish, bee stings and latex. Treatment includes antihistamines, avoiding triggers and, in some cases, immunotherapy (allergy shots) that gradually desensitise the immune system.