Thank you for the link to Wilkepedia Red_42..this is a very good link.
Atopy can be much more than just a fancy name for a rash... if you read further down the wilkepedia page you find the following statements:
"The hereditary component is presumably due to certain genes coding proteins involved in the normal immune response mechanism, i.e., human leukocyte antigen, although environmental factors have also been implicated. Atopic syndrome can be fatal for those who experience serious allergic reactions such as anaphylaxis, brought on by reactions to food or environment.
The individual components are all caused at least in part by allergy (type I hypersensitivity reactions). These responses appear after the body is exposed to various allergens, for example specific kinds of food, pollen, dander or insect venoms. Although atopy has various definitions, most consistently it is defined by the presence of elevated levels of total and allergen-specific IgE in the serum of patient, leading to positive skin-prick tests to common allergens"