Introduction
Cow´s milk protein allergy (CMPA) is the most common cause of food allergy in young children.[1] The estimated prevalence of cow’s milk allergies ranges around 2% to 3% in the first year of life and around 60% of those are IgE-mediated reactions [2, 3]. Most children will outgrow this allergy after the first years of childhood, but is estimated that 15% of them will carry this sensitivities into the 2nd decade of life and 35% of these children will have allergic reactions to other foods [3]. Children with a systemic reaction to cow’s milk should be given a hypoallergenic formula, such as an EHF or AAF. By definition, they must be tolerated by 90% of children with CMPA with a 95% CI. [4] These hypoallergenic formulas are either partially hydrolyzed, extensively hydrolyzed (short peptides below 1500 Da) or given as an amino acid based formula.
The pathophysiologic mechanism of CMPA include IgE mediated, mixed IgE-Non IgE and non IgE mediated reactions. IgE mediated Milk reactions are known to be the 3rd most common cause of food induced anaphylaxis [5]. The related mortality from anaphylaxis in children is around 1% and accounts for 0.2 % of all pediatric intensive care admissions in the USA [5]. IgE reactions are characterized by acute onset usually minutes to hours after the exposure of an allergen with various presentations. Common symptoms include skin/mucosal (urticarial rash, angioedema, flushing), respiratory symptoms (i.e, wheezing, shortness of breath, stridor), abdominal symptoms (i.e, nausea, vomiting, abdominal pain) and cardiovascular instability (i.e. low blood pressure, tachycardia)[6].
In children with a severe IgE mediated reaction to cow’s milk they may be given an EHF. In rare cases where they develop an allergic reaction to an EHF, an AA formula is then given. Although, the intolerance rates of EHF in CMA children can be approximately 10%, an immediate systemic reaction is very rare. [7]