To the Editor: The authors of the analysis on pediatric sublingual immunotherapy (SLIT) efficacy1 must be commended because they focused the analysis on the latest years and thus strongly reduced the heterogeneity of data, especially concerning the kind of extracts and the dose schedules, which is a well-known limitation of systematic reviews and meta-analyses. However, they introduce a new factor of heterogeneity, consisting of SLIT for food allergy. Indeed, systematic reviews provide reliable indications to physicians when choosing treatments in daily practice. Including immunotherapy with foods in an analysis on SLIT for respiratory allergy is confounding for specific reasons. First, SLIT with foods is not yet considered in consensus documents and guidelines, and food extracts for SLIT are not commercially available for current practice. Second, of the 2 studies included, only the trial with a peanut extract was actually based on SLIT, whereas the other is a hybrid comparing SLIT and oral immunotherapy. Such a study found better results with oral immunotherapy, but the patients lose tolerance after 6 weeks of milk avoidance. This suggests that the study treatment is comparable to specific oral tolerance induction, which was found to provide some clinical benefit,2 but once reached, the planned amount of food requires daily consumption of such food to maintain tolerance. This makes apparent that a mechanism of action different from allergen immunotherapy is working and this issue should have been discussed in the paper.
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