Definition

Noun: 1. An inappropriate and excessive immune response: A hypersensitivity reaction is a disorder where the body's immune system reacts in an exaggerated or damaging way to a substance (allergen or antigen) that is generally harmless to most people. The severity of this reaction can vary widely.

Usage

The term hypersensitivity reaction is primarily used in medical and immunological contexts to classify and describe overreactions of the immune system. It is often discussed in relation to specific triggers and categorized into types (I-IV) based on the immune mechanisms involved. * Doctors classify allergies as a type of hypersensitivity reaction. * The patient's history indicated a prior hypersensitivity reaction to penicillin.

Examples

• The skin rash was diagnosed as a delayed to the metal in her jewelry.
• Research focuses on understanding the mechanisms behind severe to certain drugs.
• A can sometimes be life-threatening, requiring immediate medical attention.

Advanced Usage

• Type I Hypersensitivity Reaction: Also known as immediate hypersensitivity, mediated by IgE antibodies (e.g., allergic asthma, anaphylaxis).
• Type IV Hypersensitivity Reaction: Also known as delayed-type hypersensitivity, mediated by T-cells (e.g., contact dermatitis, tuberculin skin test reaction).

Variants and Related Words

• Hypersensitivity (noun): The general state or condition of being overly sensitive, especially of the immune system. ( is a specific clinical event, while is the broader predisposition or condition.)
• Hypersensitive (adjective): Having a tendency to experience hypersensitivity reactions; overly sensitive.
  • The child is hypersensitive to peanuts.

Synonyms

• Allergic reaction
• Immune overreaction

Notes on Different Meanings

The core meaning of hypersensitivity reaction is strictly medical/immunological. In non-medical, figurative language, one might describe someone as having a "hypersensitive reaction" to criticism, but this is an informal analogy and not the technical use of the term.

Noun

1. an inappropriate and excessive reaction to an allergen (as pollen or dust or animal hair or certain foods); severity ranges from mild allergy to severe systemic reactions leading to anaphylactic shock