Atopy

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**Atopy**
*Classification & external resources*
ICD-10	L20
ICD-9	691

Eczema-a typical atopic manifestation

Atopy (Greek ατοπία - placelessness) or atopic syndrome is an allergic hypersensitivity affecting parts of the body not in direct contact with the allergen. It may involve eczema (atopic dermatitis), allergic conjunctivitis, allergic rhinitis and asthma. There appears to be a strong hereditary component. One study concludes that "the general risk of developing AD (3%) and atopy (7%) increases by a factor of two with each first-degree family member already suffering from atopy"^[1]. 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.

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.

Some physical attributes have been associated with atopic syndrome, although the real relationship is poorly understood:

A skin fold under the eyes termed "Dennie-Morgan folds";
A collection of short hairs at the hairline above the forehead.
Atopic syndrome is more common in red or ginger haired people.

Some symptoms, from an atopy questionnaire^[2]:

Cracks in the skin under the earlobe
Eczema
- In elbow flexures and/or hollow of the knees
- Nipple eczema
- Neurodermatitis
- Subtype Dyshidrosis
Keratosis pilaris
Perlèche
Conjunctivitis
Chronic or seasonal rhinitis