Allergic Reactions

Allergic reactions are hypersensitive responses by the body’s immune system to antigens that are recognized as foreign bodies, with subsequent formation of antibodies. There are four types of allergic reactions:

• Anaphylaxis (immediate, antigenic-induced, antibody mediated)

• Cytotoxic (antimembrane)

• Immune complex (serum-sickness like)

• Cell mediated (delayed)

In this course the discussion will be limited to the anaphylactic and cell mediated types.

For an allergic reaction to occur, the patient must have been previously exposed to the antigen (sensitizing dose). The subsequent exposure to the antigen (challenge dose) causes the reaction. The latent period (the time between the sensitizing dose and the challenge dose) when the IgE antibody is produced varies in duration. The duration and severity of the reaction will vary by the individual.¹⁰