Question

which of the following statements is true regarding a hypersensitivity reaction?

multiple choice

hypersensitivity reaction takes place during the first exposure to an antigen.

hypersensitivity reaction takes place during a second or subsequent exposure to an antigen.

hypersensitivity reaction takes place in individuals with diseases of the immune system.

hypersensitivity reaction takes place only in children.

hypersensitivity reaction takes place only in individuals with asthma.

Explanation:

Hypersensitivity reactions occur when the immune system overreacts to an antigen. During the first exposure, the immune system sensitizes (prepares). It is during the second or subsequent exposures that the actual hypersensitivity reaction (symptoms like rash, swelling, etc.) takes place. Hypersensitivity is not limited to those with immune - system diseases (many healthy people can have allergies which are hypersensitivity reactions). It is not exclusive to children (adults can have allergies too) and not only in those with asthma (though asthma can be a manifestation of a hypersensitivity reaction in some cases).

Answer:

Hypersensitivity reaction takes place during a second or subsequent exposure to an antigen.