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TOPLINE:

In preschool children who were sensitized to house dust mite (HDM) allergens but did not have any allergy symptoms, preventive sublingual immunotherapy (SLIT) induced blocking antibodies, reduced skin and basophil reactivity, limited new sensitizations, and was well tolerated.

METHODOLOGY:

• Researchers in Austria assessed whether preventive HDM-SLIT modulated immune responses in sensitized but symptom-free preschool children aged 3-5 years.
• They randomly assigned children to receive either daily HDM-SLIT (300 index of reactivity) or placebo and assessed those treated for more than 4 months. The analysis included 18 children in the HDM-SLIT and 15 children in the placebo group (40% boys).
• Blood tests, skin prick tests, and basophil activation tests were performed at baseline and at 4, 12, and 24 months to monitor levels of HDM-specific immunoglobulin (Ig)G subclasses and IgE as well as cellular reactivity.
• The primary outcome was the change in Der p1-specific IgG levels from baseline to 24 months. Treatment compliance and adverse events were assessed every 2 months.

TAKEAWAY:

• Children who received HDM-SLIT showed greater increases in Der p1-specific IgG levels from baseline to 24 months than those who received placebo (effect size, 3.11; P = .001), with greater increases already observed at 4 and 12 months (P < .01 for both).
• Children treated with HDM-SLIT showed higher HDM-specific IgG1 and IgG4 levels by 4 months than those who received placebo and maintained higher levels through 24 months (between‑group P ≤ .05 at each timepoint).
• Children treated with HDM-SLIT had smaller skin prick wheals at several dilutions and lower basophil sensitivity and reactivity than those receiving placebo. Sera from children treated with HDM-SLIT blocked HDM-induced basophil activation.
• Fewer children treated with HDM-SLIT than with placebo became polysensitized (one vs six; P = .024), and no serious treatment-related adverse events occurred.

IN PRACTICE:

“Preventive application of HDM-SLIT in sensitized nonallergic preschool children induces immunomodulatory effects (including elevated sIgG levels with blocking activity and reduced effector cell responses) early at 4 months of treatment, thereby demonstrating potential to interfere with allergy development,” the authors of the study wrote.

SOURCE:

Zsolt Szépfalusi, MD, with the Medical University of Vienna, Vienna, Austria, was the corresponding author of the study, which was published online on May 21, 2026, in Allergy.

LIMITATIONS:

This study did not reach the planned sample size, which reduced statistical power. It remained unclear whether IgG1, IgG4, or both antibody subclasses caused the blocking effect. The trial was conducted during the COVID pandemic, when hygiene measures affected the occurrence of infectious diseases.

DISCLOSURES:

This study received support from the Austrian Science Fund and Danube Allergy Research Cluster 1.0 of the state of Lower Austria. Stallergenes-Greer provided study medication and placebo. The authors declared having no conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.