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Cow's Milk Allergy (CMA) is characterised by an immunological response to the protein(s) in cow’s milk. Symptoms can appear immediately after eating (IgE-mediated) or a few hours later (non-IgE-mediated). Some healthcare professionals use the term cow's milk protein intolerance to refer to non-IgE-mediated CMA, which wrongly gives the impression that the immune system is not involved. The only intolerance to cow’s milk is lactose intolerance – a reduced ability, or in rare cases inability, to digest the sugar (lactose) in milk. It is difficult to estimate how serious the problem of CMA is worldwide as there may be ‘pockets’ of high and low prevalence. An estimated 2.0–2.5% of UK children aged 0 to three years suffer from CMA, the majority showing signs of non-IgE-mediated CMA1.
Although weaning guidelines exist for infants in general3, and for infants at high risk of developing allergic disease, there are no official guidelines on weaning infants with CA. Experts agree that for children with existing allergies, foods should be introduced individually, a few days apart, and weaning should commence with low allergenic foods (e.g. apple, pear, butternut squash, courgette). The DH also recommends that these infants, as well as those at high risk of developing food allergies, avoid highly allergenic foods (e.g. eggs, fish and nuts) until six months of age4. National levels of allergies should also be considered when devising weaning diets as these can vary between countries5.
Many foods that don’t list milk within the ingredient list still say “may contain milk due to the processing method” on the packaging. Very few children have to avoid these products, and a consultation with a dietitian is recommended to determine whether an infant needs to avoid cows’ milk completely, including “trace amounts”, or is able to tolerate foods containing a small amount6. This information is crucial as under-restriction may lead to ongoing/severe symptoms and over-restriction may impact food intake and nutritional status. Terms that indicate a product contains milk (e.g. casein, whey, lactose, cream, non-fat milk solids, etc.) will be discussed during the consultation, and a diet sheet on foods to avoid, foods to consume (e.g. those in supermarket “free from” ranges), reading labels and weaning will also be provided by the dietitian.
Preparing cows’ milk free foods at home is a more affordable and easier way of providing a cow’s milk-free diet than checking food labels when purchasing food. Parents can use ‘allergy-free’ cookbooks or ask dieticians for help modify recipes. Most companies producing hypoallergenic infant formula now provide recipe/weaning booklets for parents.
Breastfeeding mothers avoiding cows’ milk from their diet should take a daily supplement of 1000mg calcium in combination with calcium-fortified milk alternatives, and their diet should be assessed for other nutrients of concern, particularly iodine7. There is currently concern about vitamin D intake with reference to allergies in particular, and NICE recommends that women take 10μg vitamin D per day during pregnancy and while breastfeeding8. It is also important that breastfed infants commence vitamin D supplementation from six months of age, or from one month if the mother did not take vitamin D during pregnancy8.
Children and infants with CMA should be fed hypoallergenic formula of which there are two types: extensively hydrolysed formulas (based on cows’ milk but the proteins are broken down to an extent where they will not cause allergic reactions in most infants), and amino acid formulas, which should be tolerated even by those with severe CMA9. Using a suitable hypoallergenic formula should minimise any effect on total nutrient intake. However, this depends on infants consuming a sufficient amount of formula – a particular problem in children with CMA as some formulas may not be particularly palatable10. NICE8, in line with the DH, recommends that infants over six months who consume less than 500ml (1 pint) of formula milk per day take vitamin drops containing vitamins A and D (RNI 7μg/day).
Calcium and iron intake should also be assessed, taking into account food and formula intake. CMA infants aged six months and over may benefit from moving on to a Stage 2 hypoallergenic formula (where available) with added nutrients, specifically designed for their age group. Healthcare professionals should familiarise themselves with the nutrient profile of hypoallergenic formulas designed for children aged six months plus, particularly in terms of calcium, vitamin D and iron content (often lacking in the diets of food allergic children)6.
Introducing new tastes and textures in an infant with CMA plays as important a role in preventing fussy eating behaviour as it does for any infant undergoing weaning11. This can be problematic in CMA infants, as alternatives for many everyday foods (e.g. yoghurt, fromage frais, cream cheese, macaroni cheese) can be difficult to find. Although some children with CMA may tolerate soya yoghurts, they may not be suitable for 30-50% of CMA cases.
Infants should be weighed regularly by their health visitor and plotted on the UK-WHO growth charts. Length should also be measured, as children with CMA can suffer from stunted growth12. A paediatrician or paediatric allergist should be contacted if there are any concerns.
Despite the publication of three allergy guidelines13-15, practices vary across the UK and the world. There are two schools of thought:
Testing children with IgE-mediated CMA for other foods will only indicate sensitisation. Without doing food challenges in these children (another clinical dilemma in itself), this can lead to unnecessary dietary restriction.
It is known that children with CMA are more likely to develop other food allergies, and not testing children with CMA for these may lead to other severe allergic reactions at home.
Weaning children with non-IgE-mediated CMA has not been formally studied and it makes sense to trial other allergenic foods in those children with less severe symptoms. Those with more severe non-IgE-mediated allergies should be given secondary or tertiary care to obtain more specific advice.
Introduce only one new food at a time and start with foods that are known to be tolerated by the child, ideally cooked. Introduce new foods earlier during the day, observe the infant for possible allergic reactions and be clear on how to deal with allergic reactions, as directed by the healthcare professional16.