What Is a Milk Protein Allergy?

The most common allergic disease in infancy is food allergy. Since milk protein is the main food protein source in infancy, milk protein allergy is the most common in infancy. Milk protein allergy can involve various systems throughout the body, with digestive symptoms and skin symptoms as the main manifestations. Such as: vomiting, reflux, diarrhea, blood in the stool, intestinal colic, eczema, urticaria and so on.

Chinese name: Milk protein allergy

Foreign name: cow's milk allergy, CMA

Causes of milk protein allergy and common diseases

The clinical symptoms of milk protein allergy are atypical, with different clinical manifestations, which can manifest as skin, gastrointestinal, and respiratory symptoms. There have also been reports of anaphylactic shock from consumption of milk proteins. Due to immature gastrointestinal barrier function, intestinal wall structure is loose, mucosal permeability is high, the intestine's acquired immune system has limited ability to process antigens, and excessive exposure to inappropriate or inappropriate antigens destroys the intestinal mucosa's own stability. In addition, the normal intestinal flora of infants has not yet been established, which is likely to cause an immune and inflammatory reaction in the gastrointestinal mucosa, and corresponding gastrointestinal symptoms such as vomiting, diarrhea, bloating, intestinal colic, and gastrointestinal bleeding.

Differential diagnosis of milk protein allergy

Milk protein allergies need to be distinguished from some diseases because they involve more systems and have non-specific symptoms. Those with watery persistent or chronic diarrhea should be associated with lactose intolerance, celiac disease, small intestinal lymphangiectasia, congenital or acquired immunodeficiency, microvilli inclusion disease, Tufting bowel disease, congenital loss Chlorine diarrhea, congenital sodium loss diarrhea, and endocrine tumors are identified. Those with mucus and bloody stools need to be distinguished from invasive bacterial infections, parasitic infections, inflammatory bowel disease, intestinal tuberculosis, and intestinal white plug. In order for blood to be the main manifestation, it needs to be distinguished from intestinal polyps, intussusception, anal fissures, gastrointestinal vascular malformations, and peptic ulcers. In order to be the main manifestation of constipation, it needs to be distinguished from diseases such as congenital megacolon, prolonged colon, and congenital spina bifida. Those with vomiting and feeding difficulties as the main manifestations need to be distinguished from gastrointestinal malformations, gastroesophageal reflux, and congenital genetic metabolic diseases. Children with milk protein allergy need long-term follow-up to understand the prognosis, food protein-mediated bowel disease, food protein-mediated enterocolitis, food protein-mediated colitis, and eosinophilic gastroenteritis, inflammatory bowel Diseases and other diseases overlap and overlap, follow-up can reduce the incidence of missed diagnosis and misdiagnosis.

Milk protein allergy test

Milk protein allergy physical examination

The symptoms of milk protein allergy often affect the skin, digestive tract, and respiratory tract. It is necessary to observe whether the skin of the child has a rash; the distribution range of the rash; whether there is exudation; lichenification; scratches, etc. Check the abdomen for abdominal distension, lumps, bowel sounds, etc .; also check the anus, including whether the perianum is red and swollen, whether there is an anal fistula, and whether there is anal fissure; Lung auscultation with or without wheezing. In addition, it is necessary to pay attention to the growth and development of children, and to evaluate the measured values of height, weight and head circumference.

Milk protein allergy laboratory test

Laboratory tests include in vivo tests, in vitro tests, and other endoscopy tests. In vivo tests, such as skin prick test, atopic patch test, and food challenge test; in vitro tests, such as serum-specific lgE assay, serum-specific lgG assay.

1.SPT: The detection method has high sensitivity (61% ~ 83%), but low specificity (51% ~ 72%). Clinically, when the average diameter of the positive control (histamine) air mass is 3mm, the average diameter of the negative control (normal saline) air mass needs to be combined with other diagnostic methods to confirm the diagnosis. Those with positive skin scratches will have false positive results. The time of SPT test, body temperature, disease status, whether hormones and antihistamines are used, and the operator's technology and operating supplies will affect the test results.

2. APT: This test method is suitable for the diagnosis of delayed allergic reactions. First applied to children with atopic dermatitis in 1996. The patch antigen was compared with the negative control, and the patch antigen was applied to the intact skin of the back scapular region. After 48h, the appearance of erythema was positive. The study found that children with atopic dermatitis were tested with APT and SPT at the same time. The positive rate of APT in detecting delayed allergic reactions was significantly higher than SPT. Further, the combined use of SPT and APT compared with the application of APT alone was not statistically different. significance.

3. Food challenge test: The indication of the food challenge test is that for the suspected clinical history, SPT or sLgE (+), the symptoms improved after avoidance of suspicious food; the gastrointestinal symptoms are the main medical history, but SPT or sLgE ( -), Can be confirmed by challenge test. Food challenge tests include a double-blind placebo-controlled oral food challenge test, a single-blind oral food challenge test, and an open oral food challenge test. DBPCF is the gold standard for diagnosing food allergies, but it is actually difficult to achieve a fully simulated placebo. Therefore, OFC is often used clinically to help diagnosis. Babies with a high degree of suspicion of milk protein allergy should avoid milk protein first, and immediately begin to replace formula powder (such as deep hydrolysis formula and free amino acid formula, soy formula powder is generally not recommended). Since deep hydrolyzed formula powder may also cause allergic reactions due to residual allergen fragments, free amino acid formula powder is preferred. At the same time, stop using drugs (such as histamine, hormones, etc.) that can affect the test results for 1 to 2 weeks. Milk protein avoidance usually lasts 2 to 4 weeks. The baby will then be given again from a small amount (usually a lip dose, 1 drop) that does not cause symptoms, gradually increasing to a constant amount. Observe the corresponding clinical symptoms carefully before each dose increase, monitor vital signs, and stop as soon as the relevant clinical manifestations appear. After the last dose of observation in the hospital 2 hours after the end of the dose, parents can be instructed to go home to continue to observe the situation of the child. If you suspect a non-LgE-mediated food allergy, observe at home for up to 1 month. If the infant can tolerate the maximum dose, it is a non-milk protein allergy; if a reaction occurs during the challenge, it is a milk protein allergy; if it cannot complete all the doses, it is not possible to determine whether it is a milk protein allergy. Contraindications for food challenge tests include: strong skin prick test; sLgE> 95% positive predictive value; acute and chronic diseases; severe eczema; moderate to severe malnutrition; deformity; congenital disease. Diagnostic tests of food allergies in 122 allergic children aged 1 to 5 years found that skin tests (SPT, APT) and sLgE were less sensitive than food challenge tests. The food challenge test process may induce a severe allergic reaction. The initial stage must be performed in a hospital with rescue equipment and an allergy specialist. Carefully record the changes in the child's vital signs during the test.

4.sLgE: This test has high specificity, but low sensitivity. Clinically, 0.35kIU / L is the positive cut-off point, but children with gastrointestinal tract milk allergies are usually non-LgE-mediated allergic reactions. Therefore, when the result is negative, a food challenge test is needed to help diagnose . The study found that in all children, when sLgE 15kU / L, the positive predictive value was 95%; in children 2 years old, when sLgE 5kU / L, the positive predictive value was 95% [12].

5.sLgG: Although some studies suggest that this test is of significance in children with gastrointestinal symptoms as the main manifestation. But now sLgG testing has not been approved. A lot of research is needed to further clarify.

6. Endoscopy: Milk protein allergy can cause related gastrointestinal mucosal damage, which is difficult to distinguish from other diseases based on clinical symptoms alone. For children with unknown diagnosis, endoscopy can be performed when necessary to avoid misdiagnosis and misdiagnosis. .

7. Esophageal 24h impedance combined with pH detection: It is helpful for the diagnosis of eosinophilic esophagitis. The symptoms of eosinophilic esophagitis are similar to reflux esophagitis, but this test is often negative.

Milk protein allergy treatment principles

The artificially fed children were all food-avoided with non-sensitivity (free amino acid powder) or low-sensitivity (deeply hydrolyzed protein powder) formula powder, and mixed-fed children continued breastfeeding. Mothers were instructed to fast their eggs, milk, dairy products and egg products during breastfeeding, and stop using the original formula to feed with unsensitized or low-sensitivity formula. All children were given oral Bacillus subtilis bivalent live bacteria powder at the same time, and those with severe diarrhea were treated with montmorillonite powder, with regular follow-up visits.