4. Discussion
Overall, all statements were accepted by both groups of experts. However, some key differences were observed. Several organisations, such as The British Society for Allergy & Clinical Immunology (BSACI), The World Allergy Organisation and ESPGHAN encourage the development of region-specific guidelines that meet the needs of children from all social strata in the targeted countries [
11,
12,
13,
14].
CMA symptoms and indicators include cutaneous, gastrointestinal, respiratory, and systemic responses. IgE mediated CMA’s clinical symptoms appear “immediately” and occur within minutes to two hours. In a non-IgE-mediated immune reactions, the appearance of symptoms is “delayed”, and develop usually after ≥2 hours up to one week after exposure [
10,
15]. Most experts in both groups agreed that symptoms of crying, irritability and colic as single manifestations are not suggestive of CMA. However, the Middle Eastern experts tended to consider CMA as a cause of infant distress and colic compared to the European authors.
The diagnosis of CMA is based on a thorough history and physical examination. A diagnostic elimination of CM protein for one to four weeks followed by an oral food challenge or reintroduction of CM is advised when CMA is suspected [
10].
In non-exclusively breastfed infants suspected to suffer from CMA, a formula with reduced allergenicity for CM is recommended. However, formula selection is controversial and frequently influenced by availability, economics factors and scientific evidence [
1,
2,
12,
16].. At the current time, evidence is strongest for the using a CM-based eHF for the diagnostic elimination diet. The combined groups, however, failed to reach unanimous consensus on the use of eHF as the first-choice diagnostic elimination diet”, given that 3/27 authors disagreed. One rationale for recommending eHF as the first-line formula is the higher cost of AAF in the majority of countries [
17]. Nonetheless, some studies have found AAF to be comparable or more cost-effective [
12], and recommend a step-down approach. Consequently, there is a need for international guidelines to be adapted to national recommendations that take into consideration the local health system [
16].
The statement that AAF should be reserved for severe cases or patients with serious malnutrition was accepted by both expert groups. A recent review by Ribes-Koninckx et al. confirms this statement. It suggests using AAF when treatment with eHF is unsuccessful or in the case of severe CMA, particularly with associated nutritional deficiencies [
3]. IgE-mediated anaphylaxis associated with CMA, acute and chronic food protein induced enterocolitis syndrome (FPIES), multiple food allergies associated with CMA, and eosinophilic esophagitis unresponsive to a prolonged exclusion diet are a few examples [
3]. Five to ten percent of children with an IgE-mediated CMA react to eHF[
2,
3]. AAF, compared to eHF, does not contain immunogenic peptides that stimulate the immune system. Due to these negative factors, CMA and the use of AAF must be frequently re-evaluated. The patient’s age at diagnosis, symptoms, serum IgE level, and nutritional status are involved in this reassessment [
3].
Some recommendations propose a step-down strategy. In this case, AAF is used as a diagnostic elimination diet. Subsequently, an eHF is used as the therapeutic elimination diet when the OFC or reintroduction causes a relapse of symptoms. However, this approach is not frequently used, mainly for economic reasons [
10].
In Europe, formulas containing hydrolysed rice protein (HRF) have been commercially available since the 2000s as a nutritionally acceptable and well-tolerated plant-based alternative to eHF [
2]. Access to and availability of HRF are the primary factors limiting its global usage; eHFs and AAFs are the two most accessible types of substitute formulas [
12]. In addition to regional differences, there are differences in usage between specialists and non-specialists [
2]. This difference could not be demonstrated in the current manuscript because opinions of non-specialists were not collected.
One advantage of HRF is that it has a better flavour than eHF. In addition, it does not contain any residues of CM protein [
1]. In contrast, concerns have been raised regarding the arsenic content of infant rice products [
18]. Arsenic can be found in small amounts in rocks, soil, and groundwater, both inorganic and organic forms[
19]. Consequently, exposure during infancy may have potential long-term health effects, like an increased risk for developing pulmonary disease and cancer in adulthood [
19,
20]. Since 2016, the European Union has set a maximum concentration of 0.10 mg/kg for inorganic arsenic in rice intended for infants under the age of three[
21]. Hojsak et al. concluded that the arsenic concentration in HRF is low and well within the safe range established by the European Food Safety Authority, with no significant difference compared to the arsenic concentration in cow’s milk formulas [
19,
22]. However, it should be noted that not all commercially available HRF list the arsenic content on their labels [
23]. The arsenic concentration in water used to prepare the formulae, will also contribute to final arsenic content. Despite the paucity of data, the statements regarding a role for HRF as a diagnostic elimination diet were accepted by both expert groups.
[ Soy formula may also be a treatment option, but limited evidence supports its usage10]. Current soy infant formulae are nutritionally adequate and promote healthy growth and development. In the first two years of life, soy infant formula does not reduce the likelihood of allergic manifestations [
24,
25]. Cross-allergy between CM protein and soy is rare in IgE-mediated CMA; therefore, soy-based infant formula can be used as an alternative therapy diet [
26,
27]. However, it should be noted that cross-allergy is more prevalent in non-IgE-mediated CMA. The majority of data supporting this association originate from the United States. Studies conducted in the US indicate that 30 to 50% of children with FPIES react to both cow’s milk and soy, while the overwhelming majority of studies originating from outside the US indicate a much lower percentage [
10,
28]. Soy allergy prevalence ranges from 0 to 0.5% in the general population and 0 to 12.9% in allergic children [
29]. The availability of soy infant formula in many European countries has decreased in recent years. Soy infant formula can be considered as a second option when other formulae are not possible due to economic or cultural factors. Additionally, soy infant formula has a more favourable flavour and is cheaper compared to eHF[
10].
CMA is associated with intestinal dysbiosis, with reduced diversity of gut microbiota as well as a low abundance of Bifidobacteria, Lactobacilli and Bacteroides [
30]. Modulating the intestinal microbiome may be a valuable management strategy for CMA. Adding pre, pro-, syn-, or postbiotics to infant formulae could be one way to reach this goal [
31]. Several hypoallergenic formulations include pre-, pro-, syn- or postbiotics. However, due to a lack of evidence-based literature, their additional efficacy in CMA has not yet been established [
3,
31]. All ESPGHAN experts agreed there was no added value of prebiotics, probiotics and synbiotics in the efficacy of elimination diets, whereas 3 of the 14 authors of the Middle Eastern group thought there was evidence.
The 2021 Middle East Consensus Statement described that adding prebiotics and synbiotics to a therapeutic formula may improve the tolerance to CM protein by the end of the first year of life [
9]. Synbiotics can improve gut microbiota in non-IgE-mediated CMA, bringing it closer to that of a healthy newborn [
9]. Sorensen et al. described in their systematic review that combining synbiotics and AAF resulted in the same reduction of allergic symptoms and average growth as AAF alone [
31]. In addition, outcomes suggest that the observed combination of improved dysbiosis and a trend toward decreased infection, hospital admissions, and antibiotic use might be due to the intestinal microbiome’s essential role in maintaining health and disease development[
31,
32]. Several studies have demonstrated that antibiotic use in children aged 0 to 3 causes a less diverse microbiome, with a reduced abundance of Bifidobacteria, Lactobcclli and Bacteroides [
30,
33]. Because of these negative effects on the gut microbiome, antibiotic exposure during the first years of life is associated with an increased risk of developing hay fever, eczema, and food allergy later in life, according to a 2018 meta-analysis [
34]. Metsala et al. concluded that antibiotic use in children was associated with an increased risk of developing CMA [
35]. A study encompassing 30060 children up to 7 years of age, revealed that children who received three or more antibiotic treatments were more likely to develop milk allergy, non-milk food allergy and other allergies compared to children who did not receive antibiotics. The strongest associations were observed at lower ages and varied by antibiotic class [
36]. Overall, using probiotics during and after an antibiotic course may reduce the harmful impact of antibiotics on the gut flora [
34]. This could ultimately result in an economic advantage with lower costs [
31].
Several additional studies showed that the addition of Lacticaseibacillus rhamnosus GG (LGG) is a cost-effective CMA treatment. In the United States, Guest et al. found that adding LGG to eHCF was a more cost-effective strategy than eHCF alone or AAF, as it improved outcomes at a lower cost [
37]. A Spanish investigation revealed comparable results [
38]. A study by Martin et al. indicates that eHCF combined with LGG is the most cost-effective strategy for treating CMA in the United Kingdom [
39]. According to a French study by Paquete et al., the combination of eHCF and LGG was associated with longer symptom-free periods, greater immune tolerance, and reduced costs [
40].
An important limitation of this report is that only the opinion of selected experts was solicited. Gathering input from a broader range of professionals such as general paediatricians, family doctors, allergologists, dietitians, and parents, could provide a more comprehensive perspective on how CMA is addressed in clinical practice. Expanding this analysis to a larger population may uncover more noticeable differences between cultures and regions.
Conflicts of Interest
AA received allowances for educational lectures and participated in advisory boards for Abbot , Novalac, Nestlé, & Nutricia. CP: speaker/congress fee from Nestle, Hipp, Nutricia, CellTrion. CRK has participated as a consultant and/or speaker for Danone/Nutricia, Nestle Health Science and Reckitt Benckiser. NT: Speaker and/or consulting fees from Danone/Nutricia. RS: participated as a clinical investigator, and/or advisory board member, and/or consultant, and/or speaker for Abbott, Else Nutrition, Nestlé Nutrition Institute, Nestlé Health Science, NGS, Nutricia, Soremartec and Ukko. HS has participated as a clinical investigator, and/or advisory board member, and/or consultant, and/or speaker for: Arla, BioGaia, Biocodex, Danone, Dicofarm, Else, Nestlé, NNI, Nutricia, Mead Johnson. YV has participated as a clinical investigator, and/or advisory board member, and/or consultant, and/or speaker for Abbott Nutrition, Alba Health, Arla, Ausnutria, Biogaia, By Heart, CHR Hansen, Danone, ELSE Nutrition, Friesland Campina, Nestle Health Science, Nestle Nutrition Institute, Nutricia, Mead Johnson Nutrition, Pileje, Sanulac, United Pharmaceuticals (Novalac), Yakult, Wyeth. All other authors reported no conflict of interest.