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The most common allergic diseases, such as rhinitis, asthma and atopic dermatitis, are sustained by allergic inflammation, the treatment of which requires anti-inflammatory activity. Among the available treatments, allergen immunotherapy (IT) has a documented impact on allergic inflammation which persists after its discontinuation and modifies the natural course of allergy. The anti-inflammatory effects of IT, and particularly of sublingual IT (SLIT), are based on the ability to modify the phenotype of T cells which, in allergic subjects, are characterized by a prevalence of the Th2 type, with production of IL-4, IL-5, IL-13, IL-17, and IL-32 cytokines. IT-induced changes result in a Th1-type response (immune deviation) related to an increased IFN-gamma and IL-2 production or in a Th2 reduced activity, through a mechanism of anergy or tolerance. It is now known that T cell tolerance is characterized by the generation of allergen-specific Treg cells, which produce cytokines such as IL-10 and TGF-beta with immunosuppressant and/or immunoregulatory activity. Recent studies suggest that the anti-inflammatory mechanism of SLIT is similar to classical, subcutaneous IT, with a prominent role in SLIT for mucosal dendritic cells. The tolerance pattern induced by Treg accounts for the suppressed or reduced activity of inflammatory cells and for the isotypic switch of antibody synthesis from IgE to IgG, and especially to IgG4. Data obtained from biopsies clearly indicate that the pathophysiology of the oral mucosa plays a pivotal role in inducing tolerance to the sublingually administered allergen.

The natural history of allergic rhinitis (AR) is commonly characterized by worsening of symptom severity, frequent comorbidity with asthma, and polysensitization to aeroallergens. The polysensitization phenomenon starts in early childhood. AR classification has been recently revised, and some studies investigated the new types: intermittent (IAR) and persistent (PER) AR. However, no study has been carried out on children regarding this issue. This preliminary study was performed on a large cohort of children with allergic rhinitis to evaluate the type and severity of rhinitis and its possible association with asthma, including severity grade. One hundred and thirty-nine children (86 males, 53 females, mean age 11.8 years, range 3.5–17.7 years) with allergic rhinitis were prospectively and consecutively evaluated. Seventy-one children had rhinitis alone and 68 had rhinitis associated with asthma. Forty children had IAR, 30 of whom with moderate-severe grade. Ninety-nine children had PER, 65 of whom had moderate-severe grade. The severity of AR was not associated with asthma presence (Fisher ?2= 0.5765; Prob.=0.9018). Regarding asthma severity, 30 children had the intermittent form, whereas 38 had the persistent form: 15 mild, 22 moderate, and 1 severe. This study provides the first evidence concerning the ARIA classification in children, partially confirming findings obtained in adulthood.