A milk allergy is a food allergy, an adverse immune reaction to one or more of the protein constituents of milk from any animal (most commonly alpha S1-casein, a protein in cow's milk). The body manifests either an antibody-based immune response or a cell-based immune response to these allergens. Antibody responses are usually rapid and can involve anaphylaxis, a potentially life-threatening condition. Cell-mediated responses take hours to days to appear.
A wide variety of foods can cause allergic reactions, but in the United States 90% of allergic responses to foods are caused by cow's milk, eggs, wheat, peanuts, tree nuts,shellfish, fish and soy. The Food Allergen Labeling and Consumer Protection Act (FALCPA) of 2004 requires that the label of a food that contains an ingredient that is or contains protein from these eight major food allergens declare the presence of the allergen in the manner described by the law. Lists can be different in different countries. The Japanese Guideline for Food Allergy includes buckwheat and fruit in a top ten list. The European Union requires labeling for the same eight as the United States plus celery, mustard, lupin beans, sesame seeds, sulfites (used as a wine preservative) and molluscs.
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Description
Milk allergy is a food allergy, an adverse immune reaction to a food protein that is normally harmless to the nonallergic individual.
Milk allergy is a distinct from lactose intolerance, which is a nonallergic food sensitivity, due to not enough of the enzyme lactase in the small intestines to break lactose down into glucose and galactose.
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Signs and symptoms
The effects of antibody-mediated allergy are rapid in onset, evolving within minutes or seconds. These allergies always arise within an hour of drinking milk; but can occasionally be delayed longer when eating food containing milk as an ingredient. The effects of non-antibody-mediated allergy is delayed; because it is not caused by antibodies, it can take several hours, or even up to 72 hours to produce a clinical effect. The most common symptoms for both types are hives and swelling, vomiting, and wheezing, with symptoms first arising in skin, then the GI tract, and less commonly, the respiratory tract. Milk allergy can cause anaphylaxis in about 1-2% of cases, which is a severe, life-threatening allergic reaction.
Mechanism
The major allergens in cow milk are ?s1-, ?s2-, ?-, and ?-casein and the whey proteins ?- and ?-lactoglobulin. The body may raise an antibody-based immune response or a cell-based immune response to these allergens. The reaction to cow milk is caused by Immunoglobulin E (IgE) and non-IgE mediated responses, with the latter being the most frequent. The non-IgE reactions involving the gastrointestinal tract are typically delayed while IgE reactions such as hives are much more immediate.
Diagnosis
Diagnosis is carried out by first doing a diagnostic elimination diet, skin prick tests, measuring IgE in blood, and conducting in-office food challenges. A double-blind, placebo-controlled food challenge is still the gold standard for the diagnosis for all food allergies, including milk allergies. A negative IgE test doesn't rule out antibody-based allergy (in the case of false negatives), or cell-mediated allergy. Therefore, double-blind, placebo-controlled food challenge is important to rule out this form of allergy.
Prevention and treatment
The main treatment for milk allergy is avoiding dairy products. Milk from other species (goat, sheep...) should not be substituted as milk proteins from other mammals are often cross-reactive.
Dairy proteins can be found in breast milk, so nursing mothers should also abstain from dairy products. Probiotic products have been tested, and some found to contain milk proteins which were not always indicated on the labels.
Milk substitute formulas are used to provide a complete source of nutrition for infants. These include soy-based formulas, hypoallergenic formulas based on partially or extensively hydrolyzed protein, and free amino acid-based formulas such as Neocate, EleCare, and Puramino. 'Milk' substitutes from soy, rice or almonds are not appropriate for infant feeding in lieu of breast milk or infant formula, as these are not nutritionally complete, lacking many essential vitamins and minerals.
The elimination diet should be tested every six months by testing milk-containing products low on the "milk ladder", such as fully cooked foods containing milk, in which the milk proteins have been denatured, and ending with fresh cheese and milk.
Treatment for accidental ingestion of milk products by allergic individuals varies depending on the sensitivity of the person. An antihistamine such as diphenhydramine (Benadryl) may be prescribed. Sometimes prednisone will be prescribed to prevent a possible late phase Type I hypersensitivity reaction. Severe allergic reactions may require treatment with an epinephrine pen, i.e., an injection device designed to be used by a non-healthcare professionial when emergency treatment is warranted.
Outcomes
Generally, affected infants lose clinical reactivity to milk during early childhood or at latest by adolescence; around half the cases resolve within the first year and 80-90% resolve within five years.
Milk allergy is found to be associated with increased hospitalization rates and steroid use among children with asthma.
Between 13% and 20% of children allergic to milk are also allergic to beef.
Epidemiology
Milk allergy is the most common food allergy in early childhood. It affects between 2% and 3% of infants in developed countries. This estimate is for antibody-based allergy; prevalence of allergy based on cellular immunity is unknown.
Research directions
Desensitization, which is a slow process of eating tiny amounts of the allergenic protein, until the body is able to tolerate more significant exposure, results in reduced symptoms or even remission of the allergy in some people and is being explored for milk allergy. This is called oral immunotherapy. Sublingual immunotherapy, in which the allergenic protein is help in the mouth, under the tongue, has been approved for grass and ragweed allergies, but not yet for foods. A 2014 meta-analysis found oral desensitization for cow's milk allergy in children to be relatively safe and effective but found that further study was needed to understand the overall immune response to it, and questions remain open about duration of the desensitization.
There is research on probiotics as a means of treating milk allergy, but two reviews concluded that the evidence is inconsistent and cannot yet be recommended. As noted above, some probiotic products have been shown to contain milk proteins, not always indicated on the labels, and may cause an allergic reaction.
Source of the article : Wikipedia
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