Allergic rhinitis, or hay fever, is an allergic inflammation of the nasal passages. It occurs when an allergen (substance causing the allergy) is inhaled by a susceptible individual, triggering an exagerrated immune response. It usually occurs before 30 years and tends to get less serious with time. It may be seasonal, a reaction to grass, pollen from flowers, trees or weeds. It may also be a reaction to dust mites, mould, animal body products.
Attribution: Avallain