Question

A hypersensitivity reaction occurs?

1) during the first exposure to an antigen.
2) during a second or subsequent exposure to an antigen.
3) in individuals with diseases of the immune system.
4) only in children.
5) only in individuals with asthma.

Answer 1

Type I hypersensitivities occur during a second or subsequent exposure to an antigen after sensitization. The immune system releases chemical mediators upon subsequent exposure, causing allergic reactions. option 2

Step-by-step explanation:

Allergies, specifically type I hypersensitivities, occur during a second or subsequent exposure to an antigen. This immune reaction happens when an individual has been sensitized to the antigen after the initial exposure. The immune system responds by producing IgE antibodies, which bind to mast cells. Upon subsequent exposure, the antigen binds to the IgE antibodies on mast cells, triggering the release of chemical mediators, such as histamine and serotonin, which cause allergic reactions. Allergies, specifically type I hypersensitivities, occur during a second or subsequent exposure to an antigen.