Milk protein allergy is the most common food allergy among infants and children, according to the Food Allergy and Research Education website 1. Milk allergy can occur in both breast-fed and formula-fed infants. While formula-fed infants can change formulas to avoid milk protein, the mother of a breast-fed infant must alter her diet to avoid milk protein.

Milk Allergy Background Info

Milk protein allergy occurs when an infant's immune system mistakenly identifies milk protein as a foreign and potentially dangerous substance. The immune system forms an antibody known as immunoglobulin E, or IgE, specifically to the milk protein. When the infant encounters the protein in the future, the IgE recognizes it and initiates a series of events that result in the symptoms of an allergic reaction.

Sources of Milk Protein

Milk Protein Intolerance Symptoms

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The Cleveland Clinic says breastfed infants can develop milk protein allergy by exposure to the protein as it is passed through the breast milk 2. For this reason, the breastfeeding mother needs to avoid all dairy products. In addition to milk, cheese, yogurt and ice cream, less obvious dairy products such as:

• butter
  
• sour cream
  
• custard
  
• casein can contain milk protein as well

Foods such as chocolate, deli meat and hot dogs may contain milk protein, so careful analysis of food labels is necessary prior to consumption of these foods.

Elimination Time Frame

Even when the breastfeeding mother cuts milk protein out of her diet, the protein may still be expressed in her milk for up to two weeks, and it can be another two weeks before the protein is out of the infant's circulation. For this reason, dairy products must be eliminated for two to three weeks to ascertain whether a notable improvement in the infant's symptoms has been achieved. If the infant suffered from a severe reaction thought to be related to milk protein, it may be necessary for the mother to supplement with a non-milk based formula while the milk protein is eliminated from her own milk supply.

Benefits of Avoidance

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Adhering to a diet that avoids milk protein both prevents symptoms of allergy in the infant and allows the mother-baby bond of breastfeeding to continue. In addition to the short-term symptoms of an allergic reaction, an infant with a milk protein allergy may be fussy frequently and have poor weight gain. According to Kellymom.com, infants often outgrow the milk protein allergy and the mother may be able to reintroduce dairy products after six months 3. The process of re-introduction should be discussed with a physician.

Seek Expert Advice

If eliminating all sources of milk protein from the diet does not relieve symptoms in the infant, the infant may suffer from a soy protein allergy as well. In this case, eliminating all milk and soy protein from the diet will allow the mother to continue breastfeeding. A nutritionist is often helpful in this situation since a limited diet may limit the variety of foods that the mother is able to consume.