An allergy is a immune malfunction whereby a person's body is hypersensitised to react immunologically to typically nonimmunogenic substances. When a person is hypersensitised these substances are known as allergens. The word allergy derives from the Greek words allos meaning "other" and ergon meaning "reaction" or "reactivity". Reactions can vary from the benign runny nose, to life-threatening anaphylactic shock and death.

Anaphylaxis is an acute systemic (multi-system) and very severe Type I Hypersensitivity allergic reaction in humans and other mammals. The term comes from the Greek words ανα ana (against) and φύλαξις phylaxis (protection). ...