Allergen Immunotherapy for Atopic Dermatitis: A Systematic Review and Meta-Analysis of Benefits and Harms

BACKGROUND: Atopic dermatitis (AD, eczema) is driven by a combination of skin barrier defects, immune dysregulation, and extrinsic stimuli (eg. allergens, irritants, microbes). The role of environmental allergens (aeroallergens) in triggering AD remains unclear. OBJECTIVE: Systematically synthesize evidence regarding the benefits and harms of allergen immunotherapy (AIT) for AD. METHODS: As part of the 2022 AAAAI/ACAAI JTFPP AD Guideline update, we searched MEDLINE, EMBASE, CENTRAL, CINAHL, LILACS, GREAT and Web of Science (all databases) to December 2021 for randomized controlled trials (RCTs) comparing subcutaneous immunotherapy (SCIT), sublingual immunotherapy (SLIT), and/or no AIT (placebo or standard of care) for guideline panel-defined patient-important outcomes: AD severity, itch, AD-related quality of life (QoL), flares and adverse events. Raters independently screened, extracted data and assessed risk of bias in duplicate. We synthesized intervention effects using Frequentist and Bayesian random-effects models. The GRADE approach determined quality of the evidence. RESULTS: 23 RCTs including 1957 adult and pediatric patients sensitized primarily to house dust mite showed that add-on SCIT and SLIT have similar relative and absolute effects and likely result in important improvements in AD severity, defined as a 50% reduction in SCORing AD (SCORAD; RR 1.53 [95%CI 1.31-1.78]; 26% to 40%, absolute difference 14%) and QoL, defined as an improvement in Dermatology Life Quality Index (DLQI) by 4 points or more (RR 1.44 [1.03-2.01]; 39% to 56%, absolute difference 17%; both outcomes moderate-certainty). Both routes of AIT increased adverse events (RR 1.61 [1.44-1.79]; 66% with SCIT vs 41% with placebo; 13% with SLIT vs 8% with placebo; high-certainty). AIT\u27s effect on sleep disturbance and eczema flares were very uncertain. Subgroup and sensitivity analyses were consistent with the main findings. CONCLUSIONS: SCIT and SLIT to aeroallergens, particularly house dust mite, can similarly and importantly improve AD severity and QoL. SCIT increases adverse effects more than SLIT. These findings support a multidisciplinary and shared-decision making approach to optimally managing AD