*2.1. Study Group*

Participants were recruited from 1 February 2018 until 30 January 2019 among infants hospitalized in the Department of Pediatrics, Allergology and Gastroenterology, Collegium Medicum, Nicolaus Copernicus University, Poland and from Gastrological, Allergological and Nephrological Outpatient Clinics in Bydgoszcz, Poland.

Enrollment was proposed to parents of 245 infants under six months of age. Informed consent was obtained from 203 of them. Out of these patients, 104 did not fulfill the inclusion criteria, or were excluded (Table 1), and the parents of 12 failed to provide the full data needed for the study. The primary cause of disqualification from the study was receipt of known bacterial, viral or fungal infection or antibiotic treatment, either at the present time or in the previous month, due to their impact on the microbiome. The recruitment procedure is summarized in Figure 1.

2. skin infections other than atopic dermatitis

3. lactose intolerance, non-specific intestinal inflammation, celiac disease

6. genetically determined diseases (e.g., cystic

8. known bacterial, viral or fungal infection 9. antibiotic treatment, either at the present time or in the previous month (Use of systemic antibiotics four weeks before study).

5. chronic respiratory tract diseases

fibrosis, metabolic diseases)

(e.g, b scabies)

4. cancer

7. birth defects


**Table 1.** Inclusion and exclusion criteria.

Study group

Control group

recruitment procedure is summarized in Figure 1.

**Figure 1.** Study design. Flow chart depicting steps involved in patient selection and tests in this study. **Figure 1.** Study design. Flow chart depicting steps involved in patient selection and tests in this study.

disorders (CAKUT-congenital anomalies of the kidney and urinary tract), but which have not been confirmed, or children with FGIDs (functional gastrointestinal disorders), that resolved following standard treatment of symptoms and / or with a negative result for

elimination tests or oral challenge.

**Table 1.** Inclusion and exclusion criteria. **Group Inclusion Criteria Exclusion Criteria**  1. age: 0–6 months and 2. strong suspicion of FA and / or 1. immune deficiencies; autoimmunological disease Finally, 87 infants were enrolled, 59 of them with suspicion of allergies (henceforth called the "allergic group" or "study group") and 28 healthy infants, comprising the control group. The allergic group comprised 38 patients with symptoms of FA and AD (ADFA group), 16 with symptoms of FA (FA group) and 5 with AD (AD group).

inclusion criteria, or were excluded (Table 1), and the parents of 12 failed to provide the full data needed for the study. The primary cause of disqualification from the study was receipt of known bacterial, viral or fungal infection or antibiotic treatment, either at the present time or in the previous month, due to their impact on the microbiome. The

3. AD 2. skin infections other than atopic dermatitis (e.g, b scabies) 2. lactose intolerance, non-specific intestinal inflammation, celiac disease 3. cancer 4. chronic respiratory tract diseases 5. genetically determined diseases (e.g., cystic fibrosis, 1. age: 0–6 months and 2. healthy children, without symptoms indicating allergy, who were recruited among patients with suspected infection (UTIurinary tract infection) or urinary tract The characteristics of the study and control group are given in Table 2. No significant differences were observed between the FA/AD, FA, AD and control groups in terms of cesarean section, diet (breastfeeding or formula-feeding and solids intake) or family history of allergic diseases. The clinical characteristics of the studied infants are given in Table A1. In the studied group, FA was equivalent to cow's milk allergy (CMA). IgE-sensitization was found in eight (14.8%) infants.

6. birth defects

Finally, 87 infants were enrolled, 59 of them with suspicion of allergies (henceforth called the "allergic group" or "study group") and 28 healthy infants, comprising the control group. The allergic group comprised 38 patients with symptoms of FA and AD

The characteristics of the study and control group are given in Table 2. No significant differences were observed between the FA/AD, FA, AD and control groups in terms of cesarean section, diet (breastfeeding or formula-feeding and solids intake) or family history of allergic diseases. The clinical characteristics of the studied infants are given in

(ADFA group), 16 with symptoms of FA (FA group) and 5 with AD (AD group).

metabolic diseases)

weeks before study).

7. known bacterial, viral or fungal infection

8. antibiotic treatment, either at the present time or in the previous month (Use of systemic antibiotics four


## **Table 2.** Characteristics of the study and control groups.

*p*-value of Fisher's exact test is given.
