Cow’s milk contains proteins, as do many other foods, which are essential for growth and for most people are harmless. Food allergies occur when the immune system recognises a protein in food as a foreign body and triggers a response against it and histamine is released, a chemical which causes symptoms such as swelling, wheezing, hives, itching and vomiting.
Many foods cause allergies although cow’s milk protein allergy is one of the most common allergies in infants. Between 5-15% of infants will have symptoms of cow’s milk protein allergy although sever reactions are thankfully rare and estimates of the actual prevalence of this allergy are between 2-7.5% and highlights the importance of obtaining an accurate diagnosis.
Cow’s milk protein allergy (CMPA) is not an intolerance. The difference between allergy and intolerance is that an allergy involves the immune system, where as food intolerance is a difficulty in digestion, a non-allergic hypersensitivity to a particular food or element in food. This immunological involvement distinguishes CMPA from other adverse reactions to cow’s milk such as lactose intolerance, which is an intolerance to lactase, the natural sugar in cow’s milk. Congenital lactose intolerance is rare but serious condition causing faltering growth and will require a different course of treatment or diet to cow’s milk protein allergy. Symptoms of lactose intolerance are usually connected with the gastro intestinal system where as symptoms of CMPA also affects the skin and respiratory system. Therefore in order for a fast and accurate diagnosis it is important to note symptoms and timings of symptoms, keeping a food diary can help with this.
Babies can react to traces of cow’s milk proteins in breast milk although this is rare and more commonly occurs in infants that are formula fed or when weaning on to formula milks or solid food. Symptoms of an allergic reaction to cow’s milk may be immediate or delayed.
Symptoms of cow’s milk protein allergy can affect the skin, respiratory and gastrointestinal systems. Skin symptoms such as eczema are usually the predominant symptom in allergic reactions in babies where as respiratory symptoms such as rhinitis are more common in older children and adults. Immediate reactions (those occurring with in minutes and up to two hours after consumption) include acute itching, rashes, hives, vomiting, abdominal pain, diarrhoea, acute rhinitis and wheezing. Immediate symptoms make it easier to diagnose CMPA in infants, as parents are aware of what their baby has consumed immediately before the reaction. Immediate reactions can be very scary for parents and although most reactions will settle with an antihistamine, medical help should be sought. It is more difficult to link delayed symptoms to CMPA or even to link these symptoms with an allergic reaction, as they are far less obvious. Delayed symptoms can include eczema, colic, reflux, constipation or loose stools, blood in stools, catarrhal symptoms and recurrent wheeze to name just some. With a delayed reaction symptoms usually occur within 2-72 hours following ingestion of the allergen.
There is an increased likelihood of allergy where other family members suffer from allergies, asthma, eczema or hay fever. It is worth considering CMPA if your child has symptoms such as colic, reflux, eczema or constipation and the usual treatments have not worked. If your child is struggling to gain weight and has other symptoms discussed above, this may also be indicative of CMPA.
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If you think your child has an allergy to cows milk it is important you see your GP so that a diagnosis can be made. Your doctor will want to take an allergy-focused history, looking at your Childs previous history of atopic disease such as hay fever, eczema, asthma and any history of other allergies. Any family history of atopic disease is also significant. Symptoms in relation to the timing of specific foods, reactions and previous medications and treatment will also need to be discussed.
If an allergy is suspected your GP will make a referral to a paediatrician and an allergy clinic, usually based at the hospital. At this appointment allergy testing may be undertaken which involves a blood test or a skin prick test where a small drop of fluid containing the allergen is put onto the skin and the skin is gently pricked. After a short time if a red wheal appears on the skin this confirms the allergy. Its can be more difficult to diagnose CMPA where there are delayed symptoms and this is usually done by eliminating cows milk protein from the diet to see if the symptoms improve by two weeks following elimination. Cows milk and/or cows milk products then need to be introduced again and if symptoms return this confirms CMPA. It is important that this procedure is done under the guidance a dietician or doctor.
Although a diagnosis of CMPA in babies will concern parents, if treated effectively most will outgrow this allergy by 2-3 years of age. CMPA is treated by the complete elimination of cow’s milk proteins in the diet.
If babies are exclusively breastfed then the mother will need to follow a milk free diet, formula fed babies require a hypoallergenic formula milk which is only available on prescription. The first line treatment for formula fed infants is an extensively hydrolysed formula (eHF), which is a cow’s milk based formula that has been treated with enzymes in order to break down the proteins causing the allergy. If symptoms have not improved by two weeks then an amino acid formula may be the next line of treatment. Synthetic amino acids are used in this type of formula and as with eHF this can be less palatable than usual formula milks so the sooner they can be introduced the better in order for the baby to get used to the new milk.
Soya based formulas are not usually used as an alternative as children who are allergic to cow’s milk proteins may also be allergic to the proteins in Soya and also because of the presence of phyto-oestrogens and the use of glucose as a carbohydrate source. Although not usually suitable as a formula milk Soya can be used once weaned onto solid food as a useful alternative to yoghurts and cheese. Older children with CMPA can drink oat, almond, Soya and coconut milks but these are not suitable for children under two years of age as they are low in fats, protein and macronutrients.
Weaning a baby who is allergic to cow’s milk can be a daunting task for parents as many of the traditional first foods contain cow’s milk, however a paediatric dietician will be able to advise on alternative foods that will provide the essential nutrients. Processed foods contain many hidden cows milk products so the labels need to be checked for ingredients such as whey, lactoglobulin and casein. Children that have a cow’s milk allergy are more likely to have allergies to other foods (although they may develop no other allergies). More allergenic foods such as wheat, gluten, fish, selfish eggs, seeds, nuts, and peanuts (ground – no whole nuts should be given before 5 years of age due to choking risk) should be introduced one at a time and not before six months of age.
Infants usually need 6 months of being symptom free before they are re challenged with cow’s milk and this does not usually happen before 12-18 months of age and depends on the timing of diagnosis. Introducing cow’s milk back into the diet of a child with a cow’s milk allergy should only be done with appropriate guidance and this will usually be done through regular check-ups with the GP, paediatrician or dietician.
Reintroduction of cow’s milk protein using the MILK LADDER
Authors: Josie McHugh & Dr Tim Ubhi
Review date: August 2017