The Atopic March: How Eczema Can Lead to Allergies and Asthma
The Oxford Dictionary defines the term “atopic” as “a form of allergy in which a hypersensitivity reaction may occur in a part of the body not in contact with the allergen.” These reactions on the skin cause dermatitis, while reactions in the airway can cause asthma or rhinitis (sometimes called hay fever). After allergen exposure at a site like the skin, some of these immune reactions can be local, such as allergic (contact) dermatitis, but others can happen in the lungs in the case of asthma, gut in the case of food allergies and nose in the case of allergic rhinitis.
Population, statistical and mechanistic studies have repeatedly shown that atopic dermatitis (AD), asthma and allergic rhinitis often co-occur in the same individual.1 One in three children with AD will additionally develop asthma or allergic rhinitis. The risk of developing asthma increases with AD severity as more than 50% of children with severe AD also develop asthma.1 AD patients also have a high incidence of accompanying food allergies. The earlier in life AD begins and the more severe it is, the higher the association with food allergies.2 In a large study using a database of 244,776 AD and matched non-AD patients, the prevalence and incidence of other Type 2 inflammatory diseases (including asthma and rhinitis) more than doubled among children aged 0-2 years with AD compared to those without.3 A recent study of 212 AD patients aged 12-76 indicated that 69% also had rhinitis, 33% also had allergic conjunctivitis (eye-related allergies) and 29% also had asthma.4 The connectivity of AD, food allergies, asthma and rhinitis is often referred to as the atopic march.