The Hygiene theory hypothesizes that living in an overly sterile environment may have negative effects on the immune system.

The Hygiene theory hypothesizes that living in an overly sterile environment may have negative effects on the immune system. in contrast, Severe Combined Immunodeficiency (SCID) also known as "bubble boy syndrome." is a genetic condition in which leukocytes are unable to properly develop. Suppose two twins are kept in a completely sterile environment. One twin has a normal immune system, whereas the other has SCID. Discuss how each of the twins would react to an allergen like pollen compared to a bacterial infection.