Cow's milk is one of the most common food allergies in children, affecting 1 in 50 infants in Australia and New Zealand. Although most children out-grow cow's milk allergy by the age of four years, some retain the allergy for life. Cow's milk allergy may very rarely occur in adults usually involving immediate allergic reactions or eczema.
Reactions can occur immediately or up to several days after milk ingestion
Patients with allergic reactions caused by cow's milk allergy can be divided into 3 groups:
Quick onset reactors (immediate) develop symptoms within minutes or up to one hour after ingestion of small volumes of cow's milk.
Symptoms may include urticaria (hives), eczema, facial swelling, vomiting, diarrhoea, noisy breathing or wheeze. Severe reactions may result in floppiness in infants and anaphylaxis.
Diagnosis is usually obvious because of the immediate reaction and can be confirmed using allergy tests (skin prick tests or allergen specific IgE [RAST] blood tests), as they are almost always positive in these cases as the reactions are usually IgE mediated.
Slow onset reactors (intermediate) usually develop vomiting or diarrhoea several hours after ingestion of moderate amounts of cow's milk.
The mechanism for this appears to be due to inflammation of the gut and skin by white cells sensitive to milk. Allergy tests (skin prick tests or allergen specific IgE [RAST] blood tests) are not always positive in these cases as the reactions are not usually IgE mediated.
Late reactors develop eczema, vomiting, diarrhoea or asthmatic symptoms after approximately 24 hours, or up to several days after ingestion of normal volumes of cow's milk.
Allergy tests (skin prick tests or allergen specific IgE [RAST] blood tests) are rarely positive in these cases as the reactions are rarely IgE mediated, but thought to involve T-cells.
It is extremely important to note that there is no place in the diagnosis of milk allergy for unproven tests such as Vega testing, kinesiology, cytotoxic food testing, hair analysis or Alcat tests.
Reliable diagnosis is important
While the allergic nature of "immediate" reactors to milk can be confirmed using allergy tests (skin prick tests or RAST blood tests), the diagnosis of "slower reactors" is more difficult. .
Delayed allergic reactiions may be suspected in some patients from a history of ongoing skin, breathing and gut symptoms in babies. Confirmation of the diagnosis usually requires a specialist consultation which will involve allergen-specific IgE testing and frequently dietary manipulation. .
It is important that medically and scientifically proven methods are used to confirm diagnosis, including:
a) SKIN PRICK TEST (SPT)
Levels of SPT size which measure Immunoglobulin E (IgE) for specific milk proteins diagnostic of cow's milk allergy have been defined, i.e. levels with a 95% Positive Predictive Value for the diagnosis of cow's milk allergy are a SPT weal of 8mm or greater. There is no minimum age for skin testing, which can be performed in babies and infants with useful results.
b) ALLERGEN SPECIFIC IGE BLOOD TESTS (RAST)
RAST blood tests measure IgE antibodies specific for milk proteins. Levels of RAST for cow's milk have been defined with a 90% positive predictive value for diagnosing cow's milk allergy.
c) ELIMINATION AND RE-INTRODUCTION OF COW'S MILK AND PRODUCTS CONTAINING COW'S MILK FROM THE DIET
Milk allergy is confirmed if elimination results in symptomatic improvement, and re-introduction
of cow's milk causes symptoms to reappear. Such diagnostic challenges are done for limited periods only and should be performed in consultation with an allergy specialist and dietician. Prolonged dietary exclusion without clear diagnosis is not recommended.
It is important to note that elimination and re-introduction of cow's milk and dairy products should only be undertaken with specialist advice, particularly in cases with severe symptoms. Elimination of cow's milk entirely from the diet is usually difficult and needs to be done in consultation with a specialist dietician. If long term exclusion is required, patients require an alternative source of calcium and protein, and advice from a dietitian should be sought. This applies to the affected child, and to their mother if dietary exclusion during breast feeding is required.
Treatment involves avoidance of dairy products
Treatment of cow's milk allergy involves elimination of all cow's milk and dairy products from the diet and substitution with an appropriate formula. However, avoiding dairy products in children is not easy.
Parents of cow's milk allergic children should read all labels of prepared foods and avoid any food which contains cow's or goat's milk, cheese, butter, ghee, butter milk cream, cream fraiche, milk powder, whey, casein and margarine containing milk products.
Some infants who are breast fed may develop cow's milk allergy if they receive cow's milk allergens through the mother's breast milk. It may therefore be necessary to restrict dairy products in the mother's diet, and replace with a calcium supplement, if symptoms in a totally breast fed infant do not improve. Maternal diet restriction in breast feeding mothers should not be undertaken without appropriate medical and dietetic advice.
It is also nutritionally important to replace dairy products with alternative formulae, which may include:
1. Soy protein formula
Around 53-83% of cow's milk allergic children can tolerate soy-based formulae. However, between 17-47% of milk allergic children can have adverse reactions to soy, and therefore it may not be a suitable basis for an elimination diet. In children allergic to soy as well, it is not a suitable substitute. In older children, tolerance to soy allows inclusion of soy based "dairy type" products.
2. Extensively hydrolysed formula (EHF)
This is cow's milk-based formula that has been treated with enzymes to break down most of the proteins that cause symptoms in infants who are allergic to cow's milk (eg. Alfare, Pepti-Junior). These are usually supplements of first choice in milk allergic children. As the taste of hydrolysed formula may be bitter, compliance needs to be checked by a dietitian after the first few days of the elimination diet. These specialised formulae are PBS listed.
It is important to note that extensively hydrolysed formula is different to partially hydrolysed formula and the latter is not indicated as a supplement in cow's milk allergic children.
3. Amino acid based formula
Amino acid based formula (eg. Neocate, Elecare) is necessary in around ten per cent of cow's milk allergic children, who are allergic to EHF or in whom symptoms fail to respond to an elimination diet based on EHF. Diagnosis of allergy to EHF requires resolution of symptoms on commencing an amino acid based formula, followed by an oral challenge with EHF in a supervised hospital unit, to identify any immediate problems. Neocate and Elecare are PBS listed.
Some formulae are unsuitable for children with cow's milk allergy
Children allergic to cow's milk are usually allergic to a number of proteins present in dairy products. Since similar proteins are present in other animal milks such as goat's milk and horse milk, these products can also trigger allergic reactions, and should be avoided. So-called "A2 milk" (from specially bred cows) is claimed to have a number of health promoting properties, but is also unsuitable for cow's milk allergic children. Partially enzyme-treated cow's milk formula such as NAN-HA may be used to help prevent infants from developing allergies, but they are not suitable to be used as treatment for cow's milk allergic children.
Cow's milk (dairy) allergy usually resolves
Around 80% of infants will grow out of their allergy by the age of 3 years. Assessment of this likelihood and reintroduction of dairy products should be done in association with an allergy specialist. Depending on the history and severity of the original reactions, this may require further allergy testing and deliberate challenge, sometimes in a hospital setting.
There may be other food allergies, as well as milk
Cow's milk allergy may occur in association with other food allergies such as egg, soy, peanut and several other foods. This is referred to as multiple food allergy and should also be considered in an infant not responding to an diet based on substitution with extensively hydrolysed formula (EHF). Since food allergy is often and early manifestation of the "allergic march" and may be a predictor of later allergic respiratory disease, this offers medical practitioners the opportunity to discuss issues surrounding allergen avoidance and allergy prevention.
Other adverse reactions to cow's milk
Lactose intolerance is caused by the lack of the enzyme lactase, which helps to digest the milk sugar lactose. Symptoms may be similar to those of cow's milk allergy, such as diarrhoea, vomiting, abdominal pain and gas. This condition is uncomfortable but not dangerous, and does not cause rashes or anaphylaxis. Small amounts of cow's milk are usually tolerated, and yoghurts and hard cheeses are usually tolerated better than milk as they contain less or easier to digest lactose than cow's milk. Skin or blood allergy tests are negative, but if necessary the diagnosis can be confirmed by a breath hydrogen test. Treatment may involve reducing or avoiding consumption of dairy products containing lactose or substituting these with a lactose-free formula or milk.
Milk and mucus
Respiratory allergy (such as asthma and allergic rhinitis [hay fever]) is normally triggered by what we inhale, rather than what we eat. Some people complain that they have a short-lived sensation of thick mucus in the throat after drinking milk. This feeling poses no risk and is not an allergic reaction. Indeed in very young infants, runny noses are most commonly due to infection. Those who decide to avoid cow's milk because of these symptoms should still ensure a nutritionally adequate intake of calcium by selecting suitable substitutes.
Other adverse reactions to milk include:
- Eosinophilic oesophagitis
- Gastroesophogeal reflux disease (GORD) - (NB. Not all reflux is due to food allergy)
- Cow's milk sensitive oesophagitis
- Cow's milk sensitive enteropathy
- Cow's milk sensitive colitis.
These conditions all usually resolve with elimination of cow's milk and dairy products in the diet.
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© ASCIA 2010
The Australasian Society of Clinical Immunology and Allergy (ASCIA) is the peak professional body of Clinical Immunologists and Allergists in Australia and New Zealand.
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ASCIA Education Resources (AER) information is reviewed by ASCIA members and represents the available published literature at the time of review. Information contained in this document is not intended to replace professional medical advice and any questions regarding a medical diagnosis or treatment should be directed to a medical practitioner.
Content updated January 2010