An "important and deeply researched" (The Wall Street Journal) exploration of allergies, from their first medical description in 1819 to the cutting-edge science that is illuminating the changes in our environment and lifestyles that are making so many of us sick Hay fever. Peanut allergies. Eczema. Either you have an allergy or you know someone who does. Billions of people worldwide--an estimated 30 to 40 percent of the...