Milk Protein Allergy
Cow’s milk protein allergy (MPA) is the most common food allergy in early childhood and ranges from mild symptoms to life threatening anaphylaxis. The majority of children do outgrow this allergy and can drink milk and eat things with milk products after a few years.
What is the Allergen?
Cow’s milk is approximately 80% casein and 20% whey protein. A child can have an allergic reaction to any one or many of the various casein and whey proteins in milk. Heating and fermentation by bacteria tend to denature the whey protein and this is why some children can tolerate baked goods with milk in them or yogurt where bacteria has broken down the whey proteins somewhat.
This allergy often presents in infancy when a baby is given a milk protein based formula but can also happen with a solely breast fed infant if mom is consuming milk or milk products as some of the proteins can pass through the breast milk intact.
Is it Allergy?
IgE mediated reactions occur within minutes to hours after consuming milk. Itching or swelling of the mouth, lips, throat, and nasal passages, clear secretions and difficulty breathing are possible. Gastrointestinal symptoms like nausea, cramping, diarrhea and blood in the stool are also possible. There are many other ways allergy can manifest in the body. Anaphylaxis, where swelling and inflammation is severe enough to inhibit breathing is a true medical emergency and seconds count. If you are questioning anaphylaxis based on the symptoms a child or infant is displaying, you should be dialing 911. As ubiquitous as cow’s milk is in our diets, it may be surprising to know that it is the third leading cause of anaphylaxis in kids behind peanuts and tree nuts.
Anaphylaxis and acute, IgE mediated reactions are not the only kinds of MPA. Cow’s milk has been indicated in the development of Food protein-induced enterocolitis syndrome (FPIES). FPIES is a serious reaction that manifests with profuse vomiting and diarrhea. This can quickly lead to severe dehydration. Proctitis is a less severe presentation but causes bloody or mucous stools in an otherwise well appearing child.
Eczema and skin rash are also manifestations of allergy seen in MPA. Another branch of reactions includes the esophageal disorders, from gastroesophageal reflux to eosinophilic esophagitis.
Colic is a disorder without a known etiology, or cause, but MPA may present with colicky symptoms so it is something to consider.
Diagnosis is tricky. For the clearly IgE mediated reactions, skin testing or serum testing (immunocap, RAST testing) will show sensitivity. For many of the other reactions, IgE is not involved and these tests will likely be negative. We still group these reactions under allergy but diagnosis is made by the clinical presentation of the child or infant. There is no specific lab test, through a stool guiac to test for blood, even microscopic amounts, may be helpful.
Natural Course of MPA
There is good news for all types of MPA: most children will eventually outgrow this sensitization. The jury is still out on when this happens. For children without the classic IgE mediated reactions (remember these are the manifestations that happen later and in a more chronic fashion, like blood in the stool and eczematous rash, even the more serious reactions like FPIES) the allergy is usually outgrown rather rapidly, within the first two to three years of life. For IgE mediated reactions (anaphylaxis, swelling, secretions, itching), studies differ on when this allergy is fully outgrown: some point to toddlerhood and others to adolescence. Unfortunately, there is a small percentage of people who never outgrow the allergy.
Treatment and Management
The most important thing is to bring your concerns to your pediatrician or allergist early and determine what kind of allergy is happening. For those with more severe, IgE-mediated reactions, an epinephrine autoinjector must be carried at all times. You must be comfortable using it and make sure there is always an adult present who can help, wherever your infant or child is. It is important to talk to daycare providers and school nurses and make sure everyone is clear on when to use the medication.
As a primary care pediatrician, I am more likely to see the non-IgE forms of MPA, those that present with colicky symptoms, reflux, diarrhea or skin rash. Most of these reactions do not require epinephrine to be on hand. Always talk to your doctor before deciding which kind of allergy you are dealing with.
Regardless of the type of allergy, the mainstay of treatment is avoidance. For breastfeeding moms, you need to stop ingesting milk and milk products. For formula feeders, you need to move away from cow milk protein based formulas.
The first option is soy and this one isn’t bad. Many babies with MPA will do fine with soy but some will also react to the soy formula. For these infants, protein hydrolysate formulas have been created.
Protein Hydrolysate Formulas
Proteins are made of chains of amino acids, folded into three dimensional structures to carry out various jobs within the cells of our bodies. Allergy is based on a reaction and sensitization to particular molecular shapes. If you break up the protein, you break up the shape and reduce the allergenicity. Based on this line of thinking, formulas have been created which supply proteins in a broken down form, sometimes broken down all the way to the individual amino acids.
Enfamil and Similac are non-hydrolyzed cow milk or soy based protein formulas
Good-start, Gentlease are examples of partially hydrolyzed formulas
Nutramigen and Alimentum and extensively hydrolyzed formulas
Neocate is completely hydrolyzed down to the individual amino acids.
As you go down the list, these formulas become more expensive but may be required to completely eliminate the offending milk proteins. It is important to point out that they are no better than breast milk at effectively avoiding MPA, provided mom has completely eliminated cow milk and cow milk products from her own diet.
Avoidance for Mothers and Toddlers
So we have talked about baby formula and breast milk but what foods should a toddler with MPA or a breastfeeding mother of an infant with MPA avoid? Well, obviously milk. As milk is heated or cultured, the allergenicity goes down but not away. If an infant or child’s allergy is such that they tolerate yogurt or baked goods without symptoms, then there is no reason to avoid these. If the allergy is serious, IgE-related or symptoms are persistent, like blood in the stool in an otherwise healthy baby or toddler, you will need to avoid anything with milk in it, heated or not. This includes butter, yogurt and cheese. It includes other mammalian milks, like goat’s milk. It includes baked goods and even some head-scratchers like hot dogs and deli meats that may contain milk products or may have been sliced on a machine where cheese was sliced. Often artificial butter and nondairy products have some allergenicity as well, so avoid these.
We know that this allergy fades away in most kids, sometimes quite rapidly. When is the right time to try to introduce milk or milk products? For those with any serious IgE-mediated allergy, the right time is in an allergist office where precautions can be taken in the case of a reaction. The answer may be never: some parents may decide the reaction they witnessed was severe enough that they do not feel comfortable reintroducing milk.
For the majority of kids with milder symptoms, reintroduction can safely be tried at one year of age. If symptoms recur, your pediatrician may advise you to go back to milk free and try again at 18 months to 2 years old.
Matthew Toohey, MD. March 14, 2012