Cow's milk protein allergy (CMPA) is one of the most common food allergies in early childhood. The first-line treatment of CMPA is the elimination of cow's milk proteins (CMPs) from the child's or maternal diet.

Available data from the literature indicate that most children with CMPA acquire tolerance to CMPs with age. An assessment of tolerance acquisition to CMPs is commonly performed using milk ladder. However, scientific evidence regarding the effectiveness and safety of the milk ladder in children with CMPA is limited. Currently, there is no standardised milk ladder protocol, and different versions of the ladder and recommend by scientific societies in various countries.

This study aims to assess the effectiveness and safety of the 4-step milk ladder (4-ML) compared to the 6-step milk ladder (6-ML) in children with IgE-mediated CMPA. This is an open-label, randomised superiority trial with two parallel arms and a 1:1 allocation ratio.

Introducing baked milk into the diet of children with cow's milk protein allergy (CMPA) has been shown to potentially accelerate the development of tolerance to raw milk. However, there is no standardised milk ladder protocol, and different scientific societies across countries recommend varying versions.

This study aims to assess the effectiveness and safety of the 4-step milk ladder (4-ML) compared to the 6-step milk ladder (6-ML) in children with IgE-mediated CMPA.

We will perform an open-label randomised trial with two parallel arms in two departments of the same academic hospital. A total of 92 children with IgE-mediated CMPA will be allocated to introduce cow's milk into their diet according to either 4-ML or 6-ML with a 4-week break period between subsequent steps. Oral food challenge (OFCs) with tested products at each subsequent step of the milk ladder will be conducted in hospital settings. The primary outcome will be the percentage of children with tolerance to non-heated cow's milk proteins defined as no allergic reaction to non-heated cow's milk (120-240 ml depending on the age of the patient) during the last OFC; measured at the end of the 12-week observation period for the 4-ML and 20-week observation period for the 6-ML. Secondary outcomes will include the percentage of children with a negative OFC to each milk ladder step; the percentage of children with anaphylaxis (both those who were treated and who were not treated with adrenaline); the percentage of children with exacerbation of atopic dermatitis; growth; compliance; and quality of life of the caregivers and parents' anxiety about adverse events during their child's OFC.

The statistical analyses will be conducted with StatsDirect. The Mann-Whitney U test will be used to compare the means of continuous variables if non-normal distribution will be assessed. Proportions will be compared with the Fisher exact test. The difference in study groups was considered significant when the P value will be <05. The results of this study will be analyzed on the basis of intention to treat.

Inclusion Criteria:

• Age between 1 and 5 years.
• Diagnosis of IgE-mediated CMPA confirmed according to ESPGHAN guidelines, by a positive OFC with CMPs. In high-risk children (i.e., with a history of anaphylaxis), diagnosis based on positive skin prick testing and/or elevated specific IgE to CMPs is sufficient.
• On a therapeutic elimination diet for at least 6 months or up to 12 months of age.12
• Eligible regardless of the risk of systemic reaction (anaphylaxis) and asthma.
• Good overall health status.
• Parents without language barriers.
• Written informed consent signed by parents.
• Good cooperation with the child's guardians.

Exclusion Criteria:

• Uncontrolled asthma, defined as the presence of shortness of breath, chest tightness, cough, and/or auscultatory changes despite treatment.
• Signs of exacerbation of a chronic disease.
• Signs of acute infectious disease (i.e., acute runny nose, cough, subfebrile fever, or fever).
• Signs of exacerbation of another allergic disease (i.e., conjunctivitis, allergic rhinitis, atopic dermatitis).
• Anaphylaxis due to CMPs in the last 6 months.
• Used antihistamines within 3-10 days before the challenge (depending on the characteristics of the drug and the reason for use).
• Acquired tolerance to baked CMPs or higher steps of the milk ladder.
• Use of immunosuppressive drugs or immunotherapy

The results of this RCT, whether positive or negative, will be published in a peer-reviewed journal (data will be submitted to the first journal after 3-6 months from study completion). Abstracts will also be submitted to relevant national and international conferences.

The datasets used and/or generated during this study will be made available from a given author upon reasonable request, after the publication of results, no later than 3 years from the completion of data analysis.

After the publication of results, no later than 3 years from the completion of data analysis with no end date.

Upon reasonable request.