Allergy

An allergy is an immune response to a usually harmless substance that causes symptoms such as itching, swelling, or breathing difficulty. It arises when the immune system treats that substance as a threat.

Allergen: A substance that triggers an allergic immune response in a sensitized person. This is the usually harmless substance the immune system mistakenly targets.
Skin prick test: A diagnostic test that introduces small amounts of suspected allergens into the skin. A localized reaction can help identify sensitivities relevant to symptoms.
Food intolerance: An adverse reaction to food that does not arise from an immune allergy. Similar symptoms can occur without allergen-specific immune activation.
Adaptive immunity: The branch of immunity that learns specific targets and forms long-lasting immune memory. Allergic sensitization is a misdirected form of antigen-specific immune learning.
Atopic dermatitis: A chronic inflammatory skin disease marked by itch and recurring eczema. It commonly occurs within the broader pattern of allergic or atopic disease.
Immunoglobulin E: An antibody class involved in allergic reactions and defense against parasites. Allergen-specific IgE helps trigger many immediate allergic reactions.
Specific IgE test: A blood test that measures IgE antibodies directed against particular allergens. It can support allergy assessment when skin testing is unsuitable or needs supplementation.
Celiac disease: An autoimmune disorder in which gluten exposure damages the small intestine. It is immune-mediated, but differs from allergy in mechanism and tissue injury.
Antigen: A molecule or molecular structure recognized by components of the immune system. Allergens contain structures that immune receptors can recognize.
Allergic rhinitis: Nasal inflammation caused by an allergic response to inhaled substances. It is a common respiratory manifestation of allergy.

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