This is a retrospective review of data from pediatric patients treated between January 2008 through December 2013 at the Pediatric Allergy and Immunology Clinic at the CHA Gangnam Medical Center, Seoul and the CHA Bundang Medical Center, CHA University School of Medicine, Seongnam, Korea. The patients were identified from a large clinical database, if they fulfilled the inclusion criteria. The inclusion criteria for this study were children aged 0-10 years presenting with typical signs and symptoms of immediate-type food allergies, who underwent allergy testing for the following foods: hen's eggs, cow's milk, peanuts, soybeans, and wheat by measuring food-specific serum IgE, and who had more than one clinic visit during the study period. Food allergies were diagnosed based on a convincing history of reproducible signs and symptoms within 2 hours following ingestion of a single food⁷⁾ and specific IgE level to the suspected food ≥0.35 IU/mL⁸⁾. The charts of 223 children were examined; 57 children were excluded because all of their food-specific IgE levels tested were <0.35 IU/mL and 40 children were excluded because the offending food, according to their parents' report, did not match their food-specific IgE positivity. Children who presented with food allergy signs and symptoms following ingestion of a fruit or vegetable were excluded because specific IgE tests for commercially available fruit or vegetable allergens are often negative owing to structural instability⁹⁾. Thus, a total of 126 children were included for the final analysis. We divided the signs and symptoms of the children that developed within 2 hours of food intake in regard to the affected organs: (1) skin reactions, such as urticaria, rash, itching, or redness; (2) gastrointestinal reactions, including nausea, vomiting, abdominal pain, diarrhea, or bloody stool; (3) respiratory reactions, such as respiratory difficulty, dyspnea, wheezing, cough, rhinorrhea, nasal obstruction, or chest tightness; (4) isolated angioedema; (5) oropharyngeal reactions, such as itching of the mouth, tongue, and throat or lip swelling; and (6) anaphylaxis⁷⁾. Anaphylaxis was defined as signs and symptoms that developed immediately after exposure to certain foods and involved at least two major organ systems according to the established guidelines¹⁰⁾. Other clinical factors recorded included sex, age, gestational age at birth, birth weight, diet during the first 6 months of age, number of previous live births, season of birth, patient and parental history of allergic diseases including asthma¹¹⁾, allergic rhinitis-like symptoms¹²⁾, atopic dermatitis¹³⁾ and food allergy⁷⁾, and type of delivery. The Institutional Review Board reviewed and approved the study; informed consent was waived by the ethical review board because this was a retrospective analysis of stored laboratory data.

The ImmunoCAP system (Phadia AB, Uppsala, Sweden) was used for specific IgE assessment throughout the study period. Sensitization was defined as a specific IgE concentration ≥0.35 IU/mL⁸⁾.

All continuous variables are presented as mean values with standard deviation. The Student t test was used to examine the statistical differences in age, gestational age, birth weight, and total IgE levels between monosensitized and polysensitized children. The chi-square test was used to examine the statistical differences in sex, the number of siblings, diet within the first 6 months of age, seasons of birth, type of delivery, family history of allergic diseases, and comorbid allergic diseases of the subjects between groups. All statistical analyses were performed by using IBM SPSS Statistics ver. 21.0 (IBM Co., Armonk, NY, USA). All statistical tests were two-sided, and statistical significance was determined at a P value <0.05.

The demographic and clinical characteristics of the study population are presented in Table 1 (75 boys and 51 girls). The mean age of the study subjects were 1.6±1.6 years. Diets during the first 6 months of age were exclusive breastfeeding (53.4%), formula (7.8%), and mixed (38.8%). The percentage of the study subjects who were a first child was 72.1% and 49.1% of the study subjects had a parental history of allergic diseases. With respect to the child's history of allergic diseases, 57.3% of the study subjects were found to have comorbid allergic diseases such as asthma, allergic rhinitis-like symptoms, or atopic dermatitis (Table 1). There were no statistically significant differences in clinical parameters between boys and girls.

Table 2 shows the reported signs and symptoms that developed within 2 hours of ingestion of the offending food according to the afflicted organs; 90.0% of the children showed cutaneous manifestations, 10.0% with gastrointestinal reactions, 7.3% had respiratory reactions, 12.7% displayed angioedema, 5.5% with oropharyngeal reactions, and 12.7% suffered anaphylaxis. Of the young children with typical signs and symptoms of food allergies, hen's eggs (85.5%) were the most frequent food allergen, followed by cow's milk (73.3%), wheat (42.4%), peanuts (38.5%), and soybeans (33.6%).

Of the 126 children with food allergies, 38 children (30.2%) were monosensitized and 88 children (69.8%) were polysensitized. Polysensitized children were more likely to have been born in summer or fall, as opposed to monosensitized children in spring or winter, although the difference was not statistically significant (P=0.057). Polysensitized children were more likely to have parents with allergic rhinitis (43.8% vs. 20.6%, P=0.019) and to have been exclusively breastfed during the first 6 months of life when compared with monosensitized children (62.2% vs. 32.4%, P=0.005) (Table 3). The percentage of children with comorbidities, such as atopic dermatitis, allergic rhinitis-like symptoms, and asthma, was 63.6% in the polysensitized group and 42.4% in the monosensitized group (P=0.039). Polysensitized children showed higher total IgE levels when compared with monosensitized children, although the difference was not statistically significant (299.1±491.3 IU/mL vs. 180.1±345.9 IU/mL, P=0.195) (Table 3).

The multivariate logistic regression analysis was performed to determine independent relationships between polysensitization and clinical parameters in children with food allergies. The results suggest that a parental history of allergic diseases (i.e., allergic rhinitis) (adjusted odds ratio [aOR], 6.28; 95% confidence interval [CI], 1.78-22.13; P=0.004), season of birth (summer/fall) (aOR, 3.10; 95% CI, 1.10-8.79; P=0.033), and exclusive breastfeeding within the first 6 months of age (aOR, 3.51; 95% CI, 1.20-10.25; P=0.022) were significantly associated with the development of polysensitization to common food allergens in young children with immediate-type food allergies (Table 4).