All around the world, allergies are on the upsurge. Why? In search of an answer, this program travels the globe to examine the complex web of causes of what is amounting to an outright allergy pandemic. Topics include food allergies, pollution-induced asthma, allergies caused by cumulative damage to the skin due to overly aggressive hygiene, allergies to dust mites in the home and off-gassing chemicals found in new construction, and the controversial condition MCS, multiple chemical sensitivity. Also addressed are genetically induced asthma; the LEKTI antibody and its role in Netherton syndrome and the multiple allergies that partially characterize that condition; and imbalances in the antibody IGE, used by the immune system both to fight allergens and to bind to bodily parasites. Confusion of allergies with food intolerances and psychologically induced allergy-like histamine releases are considered as well. A BBC Production. (48 minutes)