Allergic Reactions: Milk Allergy
Breast milk is the lifeblood of mammals and the first food for newborns. Cow's milk, derived from bovine mammary glands, is a nutrient-rich, nearly perfect food. However, due to racial factors, individual predispositions, and other issues, some people may experience intolerance, allergies, or even related diseases when consuming milk.
Food allergies occur when the body mounts an abnormal immune response to ingested food, disrupting physiological functions and potentially causing tissue damage, leading to a range of clinical symptoms.
Some individuals with milk allergies experience symptoms like diarrhea and abdominal pain after consuming milk, yet they do not have lactose intolerance.For these individuals, milk components act as allergens capable of triggering allergic reactions. Typically, proteins are broken down into amino acids by intestinal enzymes before absorption. However, trace amounts of protein may bypass digestion and enter the bloodstream undigested, where they are recognized as allergens. Milk contains multiple proteins, with the threshold for triggering allergies ranging from below 30 milligrams to as little as 1 milligram.
When first exposed to milk, certain proteins stimulate lymphocytes to produce immunoglobulin E (IgE). This process, called sensitization, does not cause an allergic reaction.Upon subsequent exposure, these proteins bind to IgE, forming a new substance that triggers mast cells and basophils to release inflammatory mediators like histamine. This stimulates the gastrointestinal tract, causing abdominal pain, bloating, or diarrhea;It can also trigger asthma by affecting the respiratory tract. If the reaction occurs in the skin, it increases vascular permeability, causing fluid and red blood cells to leak out, resulting in hives or eczema. The human gut harbors vast numbers of bacteria, viruses, and ingested foods, all of which can potentially act as antigens.However, healthy individuals possess robust intestinal mucosal immune barriers that prevent antigen entry or regulate the body's immune response to invading antigens. If these mucosal barriers weaken or fail, antigens enter the body, triggering antibody production. Mast cells and basophils in the human body possess high-affinity receptors on their surfaces. Once exposed to corresponding antigens, they induce various allergic diseases affecting the gastrointestinal tract, respiratory system, or skin.Based on the time interval between ingestion and symptom onset, food allergies can be classified into immediate and delayed reactions. Immediate reactions typically occur within 2 hours of consuming allergenic foods and are generally more severe. Delayed reactions usually manifest hours or days after ingestion, with relatively milder symptoms.How can lactose intolerance be distinguished from milk allergy? While both conditions share similar symptoms like bloating, abdominal pain, and diarrhea, their underlying mechanisms differ. Milk allergy additionally presents with allergic manifestations such as skin itching, hives, eczema, allergic rhinitis, and stools often containing mucus and blood.Milk allergy is an immune-mediated reaction to food antigens, involving the body's immune system. Food intolerance, however, arises from the body's inability to process specific components of certain foods. It does not involve antibodies, does not trigger an immune response, and is a non-immune-mediated condition. If gastrointestinal discomfort occurs after consuming milk, a hydrogen breath test and urine galactose concentration test can confirm whether lactose intolerance is present.
In milk allergies, serum levels of food-specific IgE antibodies typically show significant elevation, and skin prick tests yield positive results. Milk allergies are not contagious but exhibit a certain genetic predisposition. If parents are allergic to a particular food, their children may also have a higher likelihood of developing allergies to that food. Research indicates that the prevalence of milk allergies averages between 2% and 5%.The incidence of infant cow's milk allergy is 2% when neither parent has a history of allergies. It can reach 20% if one parent has allergies, 43% if both parents have allergies, and as high as 72% if both parents share the same allergic symptoms. Approximately 1% to 2% of infant sensitization occurs due to food antigens entering the fetal bloodstream during pregnancy.Food antigens in breast milk can also sensitize infants. Breast milk may contain trace amounts of undigested or partially digested milk proteins that pass through the intestinal mucosal barrier into the lymphatic system. Infants with allergic tendencies may develop symptoms, which often diminish or disappear by ages 1 to 2. However, approximately one-third of affected children persist with milk allergies into childhood.Only 0.1% to 1% of adults experience milk allergy or persistent sensitivity. One study followed 100 children confirmed to have milk allergy via provocation tests over six years. By age 2, 28% had developed tolerance; this increased to 56% by age 4 and 78% by age 6.Only 22% of children remained allergic to milk. This demonstrates that while some individuals do experience allergic reactions after consuming milk, labeling milk as the "primary culprit" of allergies is an exaggeration that should not be taken lightly.
Milk contains a substance called β-lactoglobulin, which is a potent allergen. Certain individuals with allergic constitutions may exhibit allergic symptoms after drinking milk.Allergens in foods can also trigger cross-reactive allergies, meaning individuals allergic to one food may react to another containing the same allergen. This explains why people allergic to cow's milk may also react to goat's milk, animal skins, meat, or eggs. Cow's milk allergy can increase susceptibility to allergies in other foods.
Prevention and Management of Milk Allergy: Substitute milk with alternative products such as soy milk or soy-based beverages (formulated from soybeans, containing neither lactose nor milk proteins). For infants, breast milk remains the optimal choice, with exclusive breastfeeding recommended for at least six months.Women with a family history of allergies should avoid consuming these allergenic foods during pregnancy and lactation to prevent sensitization of the fetus. Women with allergic constitutions should minimize exposure to allergenic triggers during pregnancy. Food allergens must be clearly labeled in ingredient lists. The United States has established relevant regulations (the Food Allergen Labeling and Consumer Protection Act of 2004). Seek immediate medical attention for anaphylactic shock.After avoiding certain foods for approximately three years, small trial portions may be consumed. Some patients may no longer exhibit allergic symptoms, potentially due to the gradual degradation of antibodies against the original food allergens in the body.