Atopy Redefined

Introduction

In this chapter, we intend to discuss redefining the term atopy . Before we begin the process, however, we should first clearly delineate the meaning of the original term. Thus we first ask, What is atopy? and What defines atopy?

According to Merriam-Webster Dictionary online, atopy (2019) is “a genetic disposition to develop an allergic reaction (such as allergic rhinitis or asthma) and produce elevated levels of IgE upon exposure to an environmental antigen and especially one inhaled or digested.”

Another definition of atopy provided by is “a personal and/or familial tendency, usually in childhood or adolescence, to become sensitized and produce IgE antibodies in response to ordinary exposure to allergens, usually proteins.”

The , an educational and training organization of nearly 7000 members of allergists and immunologists and a trusted information source for patients, states atopy is “the genetic tendency to develop allergic diseases such as allergic rhinitis, asthma and atopic dermatitis (eczema). Atopy is typically associated with heightened immune responses to common allergens, especially inhaled allergens and food allergens”.

Historically, atopy was first described by Coca and Cooke in their article on the classification of hypersensitive phenomena. The term as they introduced it is derived from the Greek words a and topos , meaning “without” and “place,” respectively. They aimed to designate a terminology place for disorders such as hay fever and asthma ( ). While the abovementioned definitions provide a general framework of understanding atopy, detailed evidence, as delineated later in this chapter, points to a need to redefine or to subdivide this diverse group of patients who were currently categorized in the single and large disease entity of atopy. These challenging data include heterogeneous clinical manifestations, existence and nonexistence of skin barrier protein defect, presence and absence of elevated levels of serum IgE, different degrees of altered immune milieu, and favorable and unfavorable clinical responses to targeted immunomodulatory therapy. In this chapter we provide evidence to argue for such a need for redefinition or subdivision, with the focus on skin perspective.

Clear definition of atopic dermatitis

The current lack of uniform clinical definition and objective test that could unequivocally confirm the diagnosis of atopic dermatitis has led to significant differences in determination of disease prevalence, performance of prediction models, and risk factors ( ). The diagnostic criteria proposed by was deemed too complicated, and other diagnostic criteria were used in different geographic locations ( ). Since diagnostic criteria define disease entity, the effect of imperfect definition could result in misleading laboratory and clinical research data.