Atopy

Atopy is a predisposition toward developing certain allergic hypersensitivity reactions. Atopy is a predisposition toward developing certain allergic hypersensitivity reactions. Atopy may have a hereditary component, although contact with the allergen or irritant must occur before the hypersensitivity reaction can develop. Maternal psychological trauma in utero may also be a strong indicator for development of atopy. The term atopy was coined by Coca and Cooke in 1923. Many physicians and scientists use the term 'atopy' for any IgE-mediated reaction (even those that are appropriate and proportional to the antigen), but many pediatricians reserve the word 'atopy' for a genetically mediated predisposition to an excessive IgE reaction. The term is from Greek ἀτοπία meaning 'the state of being out of place', 'absurdity'. Atopy is a syndrome characterized by a tendency to be “hyperallergic”. A person with atopy typically presents with one or more of the following: eczema (atopic dermatitis), allergic rhinitis (hay fever), or allergic asthma. Some people with atopy display what is referred to as the “allergic triad” of symptoms, i.e. all three of the aforementioned conditions. People with atopy also have a tendency to have food allergies, allergic conjunctivitis, and other symptoms characterized by their hyperallergic state. Eosinophilic esophagitis is found to be associated with atopic allergies. Atopy may appear associated with an undiagnosed non-celiac gluten sensitivity. 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 of atopy are all caused at least in part by allergy (type I hypersensitivity reactions). Therefore, atopic responses appear after the body is exposed to various allergens, for example pollen, dander, dust mites, certain foods, or chemical/physical irritants. Although atopy has various definitions, in general, it is defined by the presence of elevated levels of total and allergen-specific IgE in the serum, leading to positive skin-prick tests to common allergens. Atopic reactions are caused by localized hypersensitivity reaction to an allergen. Atopy appears to show a strong hereditary component. One study concludes that the risk of developing atopic dermatitis (3%) or atopy in general (7%) 'increases by a factor of two with each first-degree family member already suffering from atopy'. As well, maternal stress and perinatal programming is increasingly understood as a root cause of atopy, finding that '...trauma may be a particularly robust potentiator of the cascade of biological events that increase vulnerability to atopy and may help explain the increased risk found in low-income urban populations.” Environmental factors are also thought to play a role in the development of atopy, and the 'hygiene hypothesis' is one of the models that may explain the steep rise in the incidence of atopic diseases, though this hypothesis is incomplete and in some cases, contradictory to findings. This hypothesis proposes that excess 'cleanliness' in an infant's or child's environment can lead to a decline in the number of infectious stimuli that are necessary for the proper development of the immune system. The decrease in exposure to infectious stimuli may result in an imbalance between the infectious-response ('protective') elements and the allergic-response ('false alarm') elements within the immune system.