National Board of Chiropractic Examiners (NBCE) Practice Test

Pruritus followed by the appearance of dermal wheals and erythema is characteristic of which type of hypersensitivity reaction?

1. Type I hypersensitivity reaction

2. Type II hypersensitivity reaction

3. Type III hypersensitivity reaction

4. Type IV hypersensitivity reaction

The correct answer is: Type I hypersensitivity reaction

Pruritus, along with the development of dermal wheals and erythema, is primarily associated with Type I hypersensitivity reactions. This type of hypersensitivity is mediated by immunoglobulin E (IgE) antibodies and occurs in response to allergens. When an individual is exposed to an allergen, IgE is produced and binds to mast cells and basophils, leading to their degranulation. This degranulation releases histamines and other inflammatory mediators, causing the classic symptoms of pruritus (itching) and the formation of wheals (raised, itchy areas on the skin) and erythema (redness of the skin). In contrast, Type II hypersensitivity involves IgG and IgM antibodies that target specific cells, typically leading to cell lysis or dysfunction. Type III hypersensitivity is characterized by immune complex formation, leading to inflammation and damage in tissues, often manifesting in systemic conditions rather than localized wheals and erythema. Type IV hypersensitivity is a delayed-type reaction mediated by T cells rather than antibodies, manifesting hours to days after exposure to an antigen, often leading to contact dermatitis or granulomatous reactions. Thus, the symptoms described align perfectly with the rapid response seen in Type