A gene linked to asthma and allergies also has a role in hepatitis A viral infections, according to a new study. This unexpected discovery has investigators speculating that a past infection with the hepatitis
A virus may protect some people from asthma and allergies.
There's been a dramatic rise in the number of people with these conditions over the past few decades, and some scientists blame it on modern society's cleanliness. In a theory labeled the hygiene hypothesis, they argue that our immune systems are no longer exposed to enough microbes early in life. This sets the stage for the body's defenses to overreact to normally harmless stimuli, causing allergies and asthma (SN: 8/14/99, p. 108: http://www.sciencenews.org/sn_arc99/8_14_99/bob2.htm).