Which among the following is an example for type I hypersensitivity reaction?
**Core Concept**
Type I hypersensitivity reactions are immediate allergic reactions mediated by IgE antibodies. These reactions involve the release of histamine and other chemical mediators from mast cells and basophils, leading to symptoms such as hives, itching, swelling, and anaphylaxis.
**Why the Correct Answer is Right**
The correct answer is an example of anaphylaxis, which is a severe, life-threatening type I hypersensitivity reaction. Anaphylaxis occurs when an allergen binds to IgE antibodies on the surface of mast cells and basophils, triggering the release of histamine and other chemical mediators. This leads to vasodilation, increased vascular permeability, and smooth muscle contraction, resulting in symptoms such as hypotension, bronchospasm, and respiratory distress.
**Why Each Wrong Option is Incorrect**
**Option A:** This is an example of type II hypersensitivity reaction, which involves the binding of antibodies to cell surface antigens, leading to cell destruction.
**Option B:** This is an example of type III hypersensitivity reaction, which involves the formation of antigen-antibody complexes that deposit in tissues, leading to inflammation and tissue damage.
**Option C:** This is an example of type IV hypersensitivity reaction, which involves the activation of T cells and the release of cytokines, leading to delayed hypersensitivity reactions such as contact dermatitis.
**Clinical Pearl / High-Yield Fact**
Type I hypersensitivity reactions are often referred to as "immediate hypersensitivity reactions" because they occur within minutes of exposure to the allergen. These reactions are mediated by IgE antibodies and are responsible for conditions such as allergic rhinitis, asthma, and anaphylaxis.
**Correct Answer:** C.