Milk Protein Allergy in Infants
Hunter, Beatrice Trum, Consumers' Research Magazine
Milk protein allergy occurs mainly in infants and young children, but rarely persists beyond three years of age. It seldom develops in adults. About 1% to 3% of infants develop milk protein allergy. Typically, the problem begins in the first year of life when cow's milk-based formula is introduced. Although sensitization to cow's milk protein can occur prenatally and in breast-fed infants, there is no convincing evidence that if the mother restricts her own intake of cow's milk during pregnancy or lactation, that cow's milk protein allergy will be prevented in the infant.
The allergic reaction is from an abnormal immunologic response to one or more of the proteins present in cow's milk. Immunoglobulin E (IgE) is the main group of antibodies produced by the allergic reaction, although other immune mechanisms also may be involved.
Cow's milk contains more than 25 different proteins. The ones most likely to be responsible for milk allergy are B-lactoglobulin, casein, lactalabumin, and bovine serum albumin.
Milk protein allergy is a distinctly different problem from lactose intolerance. (See "Lactose Intolerance," CR, March 1986.) Commonly, the two problems are confused, or thought to be merely different terms for the same problem. They are not.
If the infant is breast-fed, generally the proteins in human milk are well tolerated. However, when the infant is weaned and given formula containing cow's milk, the proteins in the cow's milk represent the first foreign antigens (allergic-producing substances that cause the body to manufacture antibodies) encountered in large amounts. At this time, the infant's digestive and immune processes are not yet fully developed, and the foreign antigen can contribute to the risk of developing milk protein allergy.
Symptoms of cow's milk protein allergy in an infant will vary and differ in the degree of severity. Generally, several symptoms are observed. They may involve gastrointestinal problems such as vomiting, diarrhea, and abdominal pain; skin problems such as atopic dermatitis or eczema, swellings, or rashes; and respiratory problems such as runny nose, chronic cough, or wheezing. Anaphylactic shock may be a rare but serious reaction.
Reactions are classified as immediate or later onset. Symptoms may begin about 45 minutes after the infant consumes a cow's milk-containing formula or food. Or, the symptoms may be delayed as long as 20 hours after the offending formula or food has been ingested.
Unfortunately, any observed symptoms do not confirm a diagnosis of milk protein allergy. Less than half of all infants with symptoms attributed to milk protein allergy are confirmed by a challenge with cow's milk. It is important that the diagnosis is accurate, in order to avoid adverse reactions and/or to prevent cow's milk being eliminated unnecessarily from the infant's diet.
At present, there is no single laboratory test that can confirm a diagnosis of cow's milk protein allergy. There are several tests available that can detect IgE antibodies to cow's milk protein or to determine if an infant's immune system is involved. These tests include prick skin tests; a blood test known as the radio-allergosorbent test (RAST), and the enzyme linked immunosorbent assay test (ELISA).
If these tests indicate milk protein allergy, and if the reactions are not severe, a medical professional may give the infant some cow's milk in increasing amounts until symptoms develop, or to learn if a common serving is tolerated. A double blind placebo-controlled food challenge test is considered to be the most conclusive method for diagnosing cow's milk protein allergy.
Along with a series of selected laboratory tests, the medical professional should take a thorough medical history, and make a complete physical examination of the infant who is suspected of reacting unfavorably to cow's milk protein. This combination of procedures can help exclude other possible causes of milk-induced symptoms (such as lactose intolerance). …