An immune system reaction to a substance that is normally harmless to most people.
An allergy occurs when the immune system recognizes a normally harmless substance, such as pollen, certain foods, medications, insect venom, or animal proteins, as a threat and mounts an inappropriate or exaggerated response.
Allergic reactions range from mild symptoms such as sneezing or itching to potentially life-threatening anaphylaxis. The specific immune mechanism varies between types of allergic reactions.
COMMONLY CONFUSED WITH
- Intolerance: an adverse reaction to a substance that does not involve the same type of immune response as an allergy.
- Hypersensitivity: a broader term for an exaggerated or inappropriate immune response; allergy is one type of hypersensitivity.
SEE ALSO
