An allergy is a reaction that happens within the body to a particular substance which is known as an allergen (1). Allergens are often things we are in contact with every day, such as pollen, food products and dyes. An allergy develops when someone reacts to an allergen that the majority of the population have no reaction to, such as peanuts.
Allergies can range from being very mild to being fatal. Very mild forms of allergic reactions are sometimes described as an intolerance rather than an allergy. Intolerances are usually related to food products, and produce a different set of symptoms to an allergy. Food intolerances mean that you may have difficulty digesting a particular food product which then causes digestive problems such as diarrhoea or stomach pains, whereas a food allergy would produce other symptoms such as swelling and itching around the mouth.
Over one quarter of people will suffer from some type of allergy during their lives, making them a very common problem (3). The milder forms of allergies and intolerances are far more common than serious or life threatening allergies. Mild allergies can usually be managed by avoiding the allergen that causes them, or using treatment such as a tablet or lotion.