The immune system is the highly complex defense mecha-nism that helps us to combat infection. In some people, the immune system wrongly identifies a nontoxic substance as an invader, and the white blood cells overreact and do more damage to the body than the invader. Thus, the allergic response becomes a disease in itself. Common responses are nasal congestion, coughing, wheezing, itching, hives and other skin rashes, headache, and fatigue. The substances that provoke allergic responses are called allergens.
Many people are allergic to mold.
Molds are microcospic living organisms, neither animal nor insect, that thrive where no other life form can. They also flourish in the air, in the soil, on dead leaves, and on other organic material. They may be destructive, but they are also beneficial. They help to make cheese, fertilize gardens, and speed decaying of garbage and fallen leaves. Penicillin is made from molds.