Milk allergy

A milk allergy is a food allergy, an adverse immune reaction to one or more of the constituents of milk from any animal (most commonly alpha S1-casein, a protein in cow's milk). This milk-induced allergic reaction can involve anaphylaxis, a potentially life-threatening condition.

Allergy

A person with milk allergy can be reactive to one of dozens of the proteins within milk. The most common one is alpha S1-casein.

Alpha S1-caseins do differ between species; but almost all commercially farmed animals produce antigenically similar milk. This explains why someone with an allergic reaction to cow's milk cannot drink sheep's or goat's milk, but can drink breast milk without an allergic reaction.

The allergy may be caused by the presence of specific milk antibodies or specific milk-sensitive lymphocytes. This gives rise to the two distinct forms of milk allergy: Antibody-mediated allergy, and Non-antibody mediated allergy.

Antibody-mediated allergy

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.

Lactose intolerance

Lactose intolerance is the inability of adults and children to digest lactose, a sugar found in milk and to a lesser extent dairy products, causing side effects. It is due to a lactase deficiency, or hypolactasia. In some (rare) cases, individuals have congenital alactasia, a total absence of lactase caused by a genetic defect, which prevents them from being able to digest lactose from infancy.

Lactose intolerant individuals have insufficient levels of lactase, an enzyme that catalyzes the hydrolysis of lactose into glucose and galactose, in their digestive system. In most cases, this causes symptoms which may include abdominal bloating and cramps, flatulence, diarrhea, nausea, borborygmi (rumbling stomach), or vomiting after consuming significant amounts of lactose. It is common for patients with inflammatory bowel disease to experience gastrointestinal symptoms after lactose ingestion, although the prevalence of lactase deficiency in this population has not been well studied.

Milk

Milk is a pale liquid produced by the mammary glands of mammals. It is the primary source of nutrition for infant mammals before they are able to digest other types of food. Early-lactation milk contains colostrum, which carries the mother's antibodies to its young and can reduce the risk of many diseases. It contains many other nutrients including protein and lactose.

As an agricultural product, milk is extracted from mammals during or soon after pregnancy. Dairy farms produced about 730 million tonnes of milk in 2011, from 260 million dairy cows. India is the world's largest producer of milk, and is the leading exporter of skimmed milk powder, yet has little to no other milk product exports. The ever increasing rise in domestic demand for dairy products and a large demand-supply gap could lead to India being a net importer of dairy products in the future. New Zealand, the European Union's 28 member states, Australia, and the United States are the world's largest exporters of milk and milk products. China and Russia are the world's largest importers of milk and milk products.