Prevalence of common sensitizing aeroallergens in patients with atopic dermatitis

Atopic dermatitis (AD) is a chronic skin disorder characterized by relapsing and remitting pruritic eczematous lesions with a preference for skin flexures [1]. Pathogenesis of AD is multifactorial including genetic and environmental factors, which vary across different racial groups [2], [3] and with different epidemiology [3], [4]. Although, the pathogenesis of atopic eczema is still debatable; it is known that aeroallergens can provoke atopic eczema in some patients [5]. Besides, one-third of patients with AD may develop asthma or allergic rhinitis. However, the association between AD and Type I sensitization is less clear when there is no history of inhalant allergy [6], [7].

Inside-out and outside-in hypotheses, two theories, have been suggested as explanation of type I hypersensitivity in AD. The inside-out hypothesis proposes that allergen is the trigger which then weakens the skin barrier and permit allergen introduction and presentation [8]. This suggest that inflammation is the cause of an impaired skin barrier, leading to increased penetration of allergens. However, the outside-in hypothesis proposes that presence of a leaky skin barrier allows allergens entrance which then elicits an immune response through allergen uptake by immature DCs in the skin surface. Barrier defects can promote type 2 immunity due to the epidermal production of alarmins (IL-33, TSLP and IL-25). Both theories will predispose to type 2 inflammation. [9].

The clinical picture of AD in adults is not classical as in children and may have different forms as nummular (discoid), prurigo-like, follicular, seborrheic dermatitis [10], [11] with erythroderma, but flexural lichenification is uncommon [12]. With the increasing prevalence of AD over the past decades, it affected approximately 15 % to 20 % of children and 1 % to 3 % of adults [4], [13]. Few studies have been published.

To the best of our knowledge, no available epidemiological studies thus far on Egyptian population. Therefore, we aimed to investigate the prevalence of most common aeroallergen sensitization in Egyptian patients with AD and possible association between degree of sensitization and the severity of dermatitis.

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