Allergy: Food- Cow's milk allergy /
Cow's milk allergy: the basics
01 What Do I Need To Know?
COW MILK ALLERGY AND INTOLERANCE
Cow's milk is one of the most common food allergies in children. It affects around 2- 7.5% of children, 2-3 % are of the immediate or IgE mediated type CMA while the remainder develop delayed symtoms and have cow's milk intolerance.
Sixty percent of of cow's milk reactions in young children are the delayed or intolerant type.
Up to 50% of children with CMA will develop allergies to other food proteins e.g. soy, egg, peanut and 50-80% will develop an allergy to one or more inhalant allergens e.g. grasses, house dust mite, dogs, cats.
MILK ALLERGENS
Milk contains many proteins and allergic symptoms can develop to one or more of the proteins. In most children no single protein accounts for all the symptoms.
The two main proteins are whey and casein. Casein is the curd that forms when milk curdles and whey is the watery fraction that remains.
The whey fraction comprises 20 5 of the milk proteins and contains alpha-lactolactalbumin and beta-lactaglobulin. Whey is most likely to produce the IgE antibodies responsible for most of the immediate reactions. The whey protein beta-lactaglobulin is altered by high heat, hence a whey sensitve person may be able to tolerate evaporated, boiled or sterilised (long life) milk or milkpowder.
Caseins consist of αS1-, αS2-, β-, and κ-caseins, and comprise the remaining 80% of milk proteins. Casein is heat stable and is the most important allergen in cheese. The harder the cheese the more casein is formed. Hence hard cheese is the least allergenic for those people with whey allergy. Extensive heating reduces but does not eliminate the allergenic nature of the casein fraction.
CROSS REACTIVITY
Cross reactivity occurs between cow's milk and goat and sheep. Goats milk whey is different to cow's milk.
Horse, donkey and camel milk has low cross reactivity. Horse and donkey cross react in 4 %.
Partially hydrolysed formula has a cross reactivity of 45-65% and sheep and goat's formula has a rate of 75%. Whereas soy formula cross reacts at a rate of 10-15 %.
CLINICAL TYPES OF COW'S MILK ALLERGY/INTOLERANCE
Immediate Cow's milk allergy or IgE mediated type
Symptoms begin within a few minutes of intake of small volumes of cow's milk. It may cause skin problems, eczema or urticaria or hives. It may lead to more serious effects of anapyhlaxis with respiratory problems, vomiting , diarrhoea or shock.
Many children out grow CMA by age 3-5 years.
Delayed Cow's milk allergy or intolerance or non IgE mediated
Symptoms develop several hours after ingestion of cow's milk and may include a variety of symptoms and clinically distinct conditions.
Symptoms include loose stools which may or may not contain blood, vomiting, gagging, food refusal, irritabilty or colic, skin rashes. Most children outgrow these symptoms by 2 years fo age.
Rechallenges are usualy started at 9- 12 months of age or until off cow's milk for 6 months.
DIAGNOSIS
Immediate Cow's milk allergy or IgE mediated type
Only this type is likely to give a positive blood (RAST) or skin (Skin prick testing) test result, as these tests detect the presence of Immunoglobulin E to cow's milk protein in the blood.
Delayed Cow's milk allergy or intolerance or non IgE mediated
Those children with delayed reactions are unlikley to have positive blood or skin tests, and diagnosis relies on an Elimination-Challenge test: relief of symptoms when milk is removed from the diet and recurrence when it is introduced.
02 What Others Say
- Australiasian Society of Clinical Immunology and Allergy
- Children's Hospital at Westmead
The information is not intended to take the place of medical advice.
Please seek advice from a qualified healthcare professional.
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Last updated: 16/11/2013