Unit D

Module 8 ~ Lesson 1


Allergies are an immune response to harmless invaders such as pollen, food, mould, and animal dander. The most common type of allergic reaction is an immediate reaction, often to environmental allergens in the air. Antibodies trigger certain cells to release histamines, which cause swelling, redness, itchy skin, runny nose and red eyes.

Other types of allergies can have a delayed response where the allergen triggers T-cells that have had previous contact with the allergen.


Vaccines are an important component of public health. Vaccines work by activating your immune system using a dead or inactive form of the virus that it is protecting you against. This stimulates the B cells and antibodies are created against the virus, despite the fact there is no real risk to the body. This is why a person might feel feverish and fatigued after a vaccination.

Memory B cells are formed and are ready to activate your immune system quickly if you are exposed to that virus again.


Watch this segment on vaccines.


Read "Immune System Disorders" on pages 298 to 299 of your textbook.