Allergology Vocabulary Quiz

An allergen is any substance that triggers an allergic reaction in a susceptible individual. Common allergens include pollen, dust mites, certain foods (such as peanuts or shellfish), animal dander, insect venom and some medications. The immune system of an allergic person mistakenly identifies the allergen as a threat and mounts an immune response causing symptoms ranging from mild sneezing to life-threatening anaphylaxis.

Anaphylaxis is a severe, potentially life-threatening allergic reaction that occurs rapidly after exposure to an allergen. It involves a widespread release of chemicals that can cause the body to go into shock. Symptoms include a sudden drop in blood pressure, narrowing of the airways, skin rash, nausea and loss of consciousness. It is treated as a medical emergency, typically with an injection of epinephrine (adrenaline).

Immunotherapy (also called allergen immunotherapy or desensitisation therapy) is a long-term treatment that gradually reduces the immune system's sensitivity to a specific allergen. It involves exposing the patient to progressively increasing doses of the allergen over three to five years. The aim is to retrain the immune system to tolerate the allergen without triggering a reaction.

Sensitisation is the process by which the immune system first encounters an allergen and develops a specific immune response, producing IgE antibodies. After sensitisation, subsequent exposures to the same allergen can trigger allergic symptoms. A person may be sensitised without having clinical allergy. It is detected through skin prick tests or blood tests measuring allergen-specific IgE.

Urticaria (commonly known as hives) is a skin condition characterised by raised, itchy welts that appear suddenly. It can be triggered by allergens such as foods or medications, or by physical factors such as heat or cold. Each wheal typically fades within 24 hours. When urticaria is accompanied by deeper tissue swelling, it is called angioedema.

Atopy is the genetic predisposition to develop allergic diseases such as asthma, hay fever, eczema and food allergies. Atopic individuals produce elevated levels of IgE antibodies in response to common environmental allergens. Atopy often runs in families and is associated with the 'atopic march', in which one condition may precede or accompany another during a person's lifetime.

Epinephrine (adrenaline) is the first-line treatment for anaphylaxis. When injected, it constricts blood vessels, reduces airway swelling, raises blood pressure and reverses the life-threatening effects of the reaction. People at risk of anaphylaxis are advised to carry an auto-injector (such as an EpiPen) and inject it at the first signs of a severe reaction.

Hypersensitivity refers to an excessive immune response to a usually harmless antigen that results in tissue damage or symptoms. There are four types (I–IV), classified by mechanism. Type I (IgE-mediated) is the most common form of allergy. In everyday language, hypersensitivity is often used interchangeably with allergy, but in medicine it has a broader meaning.

Allergic rhinitis is inflammation of the nasal passages caused by an allergic reaction to airborne allergens such as pollen, dust mites or pet dander. Symptoms include a runny or blocked nose, sneezing and itchy eyes. Seasonal rhinitis (hay fever) is triggered by pollen, while perennial rhinitis occurs year-round due to indoor allergens.

Tolerance is the immune system's ability to recognise a substance as harmless and not mount a reaction against it. In allergy, developing tolerance means the immune system stops reacting to a previously problematic allergen. Oral immunotherapy for food allergies aims to induce tolerance by gradually increasing the amount consumed under medical supervision.