Milk allergy is an immune hypersensitivity, an adverse immune reaction to one or more of the protein constituents of cow's milk. Symptoms can be rapid or gradual in onset. The former may include anaphylaxis, a potentially life-threatening condition which requires treatment with epinephrine. The latter can take hours to days to appear. Presentations may include atopic dermatitis, inflammation of the esophagus, enteropathy involving the small intestine and proctocolitis involving the rectum and colon.
In the United States, 90% of allergic responses to foods are caused by eight foods: cow's milk, eggs, wheat, shellfish, peanuts, tree nuts, fish, and soy beans. Allergy to cow's milk is the most common. 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. Dairy foods are also on the mandatory labeling list in Japan and the European Union.
Video Milk allergy
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 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.
Maps Milk allergy
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.
Mechanisms
Conditions caused by food allergies are classified into three groups according to the mechanism of the allergic response:
- IgE-mediated (classic) - the most common type, manifesting acute changes that occur shortly after eating, and may progress to anaphylaxis
- Non-IgE mediated - characterized by an immune response not involving immunoglobulin E; may occur hours to days after eating, complicating diagnosis
- IgE and non-IgE-mediated - a hybrid of the above two types
Allergic reactions are hyperactive responses of the immune system to generally innocuous substances, such as proteins in the foods we eat. Why some proteins trigger allergic reactions while others do is not entirely clear, although in part thought to be due to resistance to digestion. Because of this, intact or largely intact proteins reach the small intestine, which has a large presence of white blood cells involved in immune reactions. The heat of cooking structurally degrades protein molecules, potentially making them less allergenic. The pathophysiology of allergic responses can be divided into two phases. The first is an acute response that occurs immediately after exposure to an allergen. This phase can either subside or progress into a "late-phase reaction" which can substantially prolong the symptoms of a response, and result in more tissue damage.
In the early stages of acute allergic reaction, lymphocytes previously sensitized to a specific protein or protein fraction react by quickly producing a particular type of antibody known as secreted IgE (sIgE), which circulates in the blood and binds to IgE-specific receptors on the surface of other kinds of immune cells called mast cells and basophils. Both of these are involved in the acute inflammatory response. Activated mast cells and basophils undergo a process called degranulation, during which they release histamine and other inflammatory chemical mediators called (cytokines, interleukins, leukotrienes, and prostaglandins) into the surrounding tissue causing several systemic effects, such as vasodilation, mucous secretion, nerve stimulation, and smooth-muscle contraction. This results in runny nose, itchiness, shortness of breath, and potentially anaphylaxis. Depending on the individual, the allergen, and the mode of introduction, the symptoms can be system-wide (classical anaphylaxis), or localized to particular body systems; asthma is localized to the respiratory system while eczema is localized to the skin.
After the chemical mediators of the acute response subside, late-phase responses can often occur due to the migration of other white blood cells such as neutrophils, lymphocytes, eosinophils, and macrophages to the initial reaction sites. The is usually seen 2-24 hours after the original reaction. Cytokines from mast cells may also play a role in the persistence of long-term effects. Late-phase responses seen in asthma are slightly different from those seen in other allergic responses, although they are still caused by release of mediators from eosinophils.
Six major allergenic proteins from cow's milk have been identified: ?s1-, ?s2-, ?-, and ?-casein from casein proteins and ?-lactalbumin and ?-lactoglobulin from whey proteins. There is some cross-reactivity with soy protein, particularly in non-IgE mediated allergy. Heat can reduce allergenic potential, so dairy ingredients in baked goods may be less likely to trigger a reaction than milk or cheese. Non-IgE-mediated responses are more common than IgE-mediated. The former can manifest as atopic dermatitis and gastrointestinal symptoms, especially in infants and young children. Some will display both, so that a child could react to an oral food challenge with respiratory symptoms and hives (skin rash), followed a day or two later with a flare up of atopic dermatitis and gastroinstestinal symptoms, including chronic diarrhea, blood in the stools, gastroesophageal reflux disease (GERD), constipation, chronic vomiting and colic. If not diagnosed, continued infant feeding with milk protein formula can lead to iron deficiency anemia, protein-losing enteropathy with hypoalbuminemia and poor growth.
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
Dairy proteins can be found in breast milk, so nursing mothers may need to abstain from dairy products if their nursing infant is presenting with allergy symptoms.
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.
Treatment
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.
Avoiding dairy
Most people find it necessary to strictly avoid any item containing dairy ingredients. Milk from other species (goat, sheep...) should not be substituted for cow's milk, as milk proteins from other mammals are often cross-reactive. Beyond the obvious (anything with milk, cheese, cream, butter or yogurt in the name), food ingredient lists need to be examined:
Probiotic products have been tested, and some found to contain milk proteins which were not always indicated on the labels.
Epidemiology
Incidence and prevalence are terms commonly used in describing disease epidemiology. Incidence is newly diagnosed cases, which can be expressed as new cases per year per million people. Prevalence is the number of cases alive, expressible as existing cases per million people during a period of time. Milk allergies are usually observed in infants and young children, and often disappear with age (see Prognosis), so prevalence of egg allergy may be expressed as a percentage of children under a set age. Milk allergy 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.
For all age groups, a review of fifty studies conducted in Europe estimated 6.0% for self-reported milk allergy and 0.6% for confirmed. National survey data in the United States collected 2005-2006 showed that from age six and older, the prevalence of serum IgE confirmed milk allergy was under 0.4%.
Prognosis
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.
Research
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 held 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 recommended 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 three 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.
Society and culture
Whether food allergy prevalence is increasing or not, food allergy awareness has definitely increased, with impacts on the quality of life for children, their parents and their immediate caregivers. In the United States, the Food Allergen Labeling and Consumer Protection Act of 2004 causes people to be reminded of allergy problems every time they handle a food package, and restaurants have added allergen warnings to menus. The Culinary Institute of America, a premier school for chef training, has courses in allergen-free cooking and a separate teaching kitchen. School systems have protocols about what foods can be brought into the school. Despite all these precautions, people with serious allergies are aware that accidental exposure can easily occur at other peoples' houses, at school or in restaurants. Food fear has a significant impact on quality of life. Finally, for children with allergies, their quality of life is also affected by actions of their peers. There is an increased occurrence of bullying, which can include threats or acts of deliberately being touched with foods they need to avoid, also having their allergen-free food deliberately contaminated.
See also
- Food allergy (has images of hives, skin prick test and patch test)
- List of allergens (food and non-food)
- Milk soy protein intolerance
References
External links
- Milk Allergy at Food Allergy Initiative
Source of article : Wikipedia
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