Atopy

Also known as atopic syndrome.

 

Physiology

IgE and eosinophils are tools used by the immune system to fight macroparasitic diseases such as helminthiasis. IgE binds to an allergen and activates basophils, to release products including histamine. This causes a type 1 hypersensitivity reaction, also known as an allergic reaction. The size of the reaction can range from local symptoms (localised swelling, itching and redness), to systemic symptoms (angioedema, anaphylaxis).

Pathophysiology

A patient with atopy has a predisposition to produce high circulating levels of immunoglobulin E (IgE) and eosinophilia.

An atopic patient will usually have a history of one or more atopic diseases (see below). There are genetic factors, and there is often a strong family history of atopy.

This is a very common condition in highly developed societies. The hygiene hypothesis postulates that a low prevalence of parasitic infections causes a high prevalence of atopic disease, because there is insufficient modulation of the immune system without parasitic infection.

Atopic diseases

• Allergic rhinitis 
• Allergic conjunctivitis  
• Angioedema or anaphylaxis  
• Asthma
• Atopic dermatitis
• Drug allergy
• Eosinophilic esophagitis 
• Food allergy
• Urticaria

Atopy is associated with a rare vasculitis called eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome).