Background/Objectives: We aimed to evaluate the etiologic distribution of markedly elevated IgE (≥2000 IU/mL) and the association of parasitic infections with longitudinal IgE dynamics and National Institutes of Health Hyper-IgE Syndrome (NIH-HIES) score trajectories in pediatric patients. Methods: We retrospectively enrolled 127 pediatric patients with IgE ≥2000 IU/mL and ≥1 year of longitudinal follow-up at a tertiary allergy clinic (2019–2024). The primary outcome was the IgE reduction percentage difference between parasitic and non-parasitic groups. Results: Atopic sensitization was identified in 81.0% of tested patients; genetic evaluation was performed in 40 patients (31.5%), with confirmed IEI in one patient (0.8% of the cohort; 2.5% of those evaluated). Parasitic infections were present in 24.4% of patients (n = 31; intestinal parasites 15.7%, scabies 8.7%, hydatid cyst 1.6%; two patients had concurrent intestinal parasitosis and scabies). Median IgE reduction was 63.8% vs. 27.0% in parasitic versus non-parasitic groups (p < 0.001), persisting after multivariable adjustment (p < 0.001). Parasitic infection independently predicted IgE normalization below 2000 IU/mL (OR = 8.26; 95% CI: 2.76–24.68; p < 0.001). All three NIH-HIES inflammatory components (IgE, eosinophilia, eczema) regressed more often in the parasitic group (all p ≤ 0.01); no patient reached the ≥40-point HIES threshold. Conclusions: Parasitic infections produce a clinical phenotype overlapping with hyper-IgE syndrome, constituting a reversible phenocopy of primary immune dysregulation. In populations with substantial parasitic prevalence, parasitological evaluation may be a useful consideration in children with markedly elevated IgE and indeterminate clinical scores; however, this approach should complement rather than replace comprehensive clinical assessment.

Objective: This study aimed to systematically evaluate pediatric patients referred with suspected penicillin allergy and determine the rate of confirmed penicillin allergy.Materials and Methods: A retrospective study was conducted on 57 patients who presented to the Pediatric Allergy and Immunology Department of Istanbul Kanuni Sultan Süleyman Training and Research Hospital with suspected penicillin allergy between August 2023 and August 2025. All patients underwent specific IgE testing for amoxicillin, ampicillin, penicillin G, and penicillin V. Skin testing was performed in patients with parenteral drug reactions. Oral drug provocation testing was conducted in patients with negative specific IgE and skin tests.Results: The mean age was 7.4±4.9 years (median: 6 years). The most common suspected drug was amoxicillin-clavulanate (77.2%). Urticaria/angioedema (61.4%) was the most frequent reaction type. Specific IgE positivity was detected in only 3 patients (5.3%). Drug provocation testing was performed in 53 patients, with 51 patients (96.2%) tolerating the drug without complications and 2 patients (3.8%) showing positive reactions. Penicillin allergy was confirmed in 6 patients (10.5%), whereas it was excluded (delabeled) in 51 patients (89.5%).Conclusion: Our study demonstrated that 89.5% of penicillin allergy labels were incorrect. The low sensitivity of specific IgE testing was confirmed. Direct drug provocation testing is safe and effective in low-to-moderate-risk patients.