For suspected cow's milk protein allergy, why is trial use of hydrolyzed or free amino acid containing formula recommended instead of soy-based formula?

• A. Soy protein is always tolerated
• B. A percentage of children allergic to cow's milk protein are also allergic to soy protein
• C. Soy formula improves growth
• D. Soy formulas are more expensive

Answer: (B)

When suspected cow's milk protein allergy is present, the goal is to feed with a formula that has minimal allergen exposure. A portion of infants with CMPA also have a concurrent allergy to soy protein, so starting with a soy-based formula can provoke or perpetuate allergic reactions in those children. Extensively hydrolyzed formulas break cow milk proteins into small peptides, greatly reducing allergenicity, and amino acid–based formulas contain no intact protein, making them the safest option to assess tolerance and manage symptoms. If soy were used first, you might miss ongoing reactions or misattribute improvement to other factors. The other choices don’t reflect the reason for avoiding soy—growth or cost aren’t the primary clinical concerns here, and soy is not guaranteed to be tolerated by all CMPA patients.