Eosinophilic esophagitis and inhalant antigens: Pointing out the roles of allergic rhinitis, immunotherapy and biologic treatment

Eosinophilic esophagitis (EoE) and allergic rhinitis (AR) usually represent the latest manifestations of the atopic march, sharing a common type 2 inflammation response. A relevant prevalence of AR in EoE cohorts has been widely confirmed. An increasing literature assessed the involvement of aeroantigens in EoE pathogenesis, focusing foremost on the seasonality of new diagnoses, symptoms, and response to therapy. Unfortunately, no diriment direction has been achieved, probably due to the retrospective design of the studies so far available, which chose surrogate markers of EoE activity (mostly the date of new diagnosis) which may be affected by geographical, logistic and personal factors, probably not dependent by the disease itself. EoE exacerbations reported in the context of the pollen levels (preferably pollen counts) may represent a more reliable marker. AR might promote the onset and the re-exacerbation of EoE through mechanisms that are both local (ie, massive exposure to airborne antigens mediated by post-nasal drip) and systemic (type 2 inflammation). Furthermore, AR may facilitate EoE onset by predisposing to pollen food allergic syndrome (PFAS), and EoE patients with PFAS reported higher rate of AR, thus suggesting a bond among these 3 conditions whose causative relationship have still to be ascertained. In addition, because of its shifting activity from Th2 to Th1 inflammation, several case reports focused on the effect of allergen immunotherapy (AIT) employed to treat AR in EoE patients. Also in this instance, no certainties could be guaranteed, although sublingual immunotherapy (SLIT) is more frequently reported to exacerbate EoE, while SCIT is mostly described as a remission adjuvant. The real life experience reported from our allergy service appears to confirm such hypothesis. Finally, a watchful eye should be reserved to monoclonal antibodies as a potential future option for concomitant EoE and AR. In light of all this, an attentive evaluation of allergic history of EoE patients should be relevant. Future perspectives should be addressed on prospective studies targeted to shed light on causative relations among airborne antigens, AR and EoE, and to viable comprehensive treatments.