Billions of people worldwide-an estimated 30 to 40 percent of the global population-have some form of allergy. Even more concerningly, over the last decade, the number of people diagnosed with allergy has been steadily increasing, an ever-growing medical burden on individuals, families, communities, and health care systems. Medical anthropologist Theresa MacPhail, herself an allergy sufferer set out to understand why. This book is a holistic examination of the phenomenon of allergies, from their first medical description in 1819 to the mind-bending recent development of biologics and immunotherapies that are giving the most severely impacted patients hope. This is the story of allergies: what they are, why we have them, and what that might mean about the fate of humanity in a rapidly changing world. Because understanding what is irritating us and why will help us to craft better environments in the future-so we can all breathe easier.