Formula milk allergy commonly refers to cow's milk protein (CMP) allergy and affects 2 to 7.5 percent of babies, notes a study on CMP allergies in infants in the journal "Archives of Disease in Childhood." CMP allergies may also occur in breast-fed babies if milk proteins from a mother's diet passed through her breast milk. Most children will outgrow cow's milk protein allergy by 3 to 5 years old, but a minority may have a persistent allergy onto adulthood.
Cause
Two proteins in milk can cause an allergic reaction: casein, found in the curdled part of milk, and whey, the liquid part left after milk curdles. The immune system of a baby with a CMP allergy treats the proteins as harmful and releases chemicals and antibodies that identify those particular proteins. The next time the infant drinks cow's milk protein in breast-fed or formula milk, the immune response triggers an allergic reaction.
Symptoms
An infant with an allergy to cow's milk protein may experience initial symptoms within the first few months of his life. It may develop quickly, immediately after drinking milk, or seven to 10 days later. According to the "Archives of Disease in Childhood," the most frequent symptoms of cow's milk protein allergy include vomiting, diarrhea, constipation, bloody stool, eczema rash, swelling of the lips or eyelids, hives, runny nose, wheezing and chronic coughing. However, cow's milk protein allergy may be difficult to diagnose as these symptoms also occur with other health conditions affecting young babies.
Risk Factors
Infants are at higher risk of developing cow's milk protein allergy if one or both parents and/or siblings have a history of food allergies, hay fever, asthma or eczema. Infants with eczema are also more likely to develop a milk allergy, according to the Mayo Clinic. A formula-fed infant is at higher risk of developing cow's milk allergy than one who is exclusively breast-fed, notes KidsHealth, a resource site of the Nemours Foundation.
Cross-reactivity
According to the Mayo Clinic and KidsHealth, infants who are allergic to cow's milk formula may also develop allergic reactions to goat's, sheep's or buffalo milk, a complication known as cross-reactivity. Similarities between allergenic protein in these mammals and cows may trigger antibodies into eliciting the same allergic reaction. Some infants with a CMP allergy may also develop allergies to soy milk protein.
Management
The "Archives of Disease in Childhood" recommends exclusive breast-feeding for the first four months of life and completely eliminating cow's milk protein from the infant's or mother's milk as the best ways to avoid developing or exacerbating a CMP allergy. This may be a difficult task as milk is a common ingredient in many foods. KidsHealth has a list of foods that might contain milk and may be helpful in identifying food labels for milk-based ingredients (see Resources). The Mayo Clinic advises switching from cow's milk formula to soy protein or hypoallergenic formula.
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