Hypoallergenic milk formulae7


CMA in the first year of life is one of the most common problems faced by paediatricians. It is mediated by an immune mechanism, whereas cow's milk intolerance is due to non-immunological causes such as lactase deficiency. CMA may affect the gastrointestinal tract, respiratory tract, skin or blood, and systemic reactions, including anaphylaxis, may occur. Avoidance is the mainstay of treatment, and breast-feeding should be actively encouraged. Since intact cow's milk protein can pass into the breast milk, the lactating mother should avoid the excessive intake of milk products herself and take a calcium supplement. If breast-feeding is not feasible or if supplements are required, soya milk, hydrolysate or amino acid-based formulae may be used.

Hydrolysed formulae

According to the definition of the European Scientific Committee for Food, hypoallergenic or hypoantigenic formulae are those which contain hydrolysed protein. The peptides of HF should be as short as possible. In extensively hydrolysed formulae (eHF) 95% of peptides have a molecular weight below 1500 dalton and less than 0.5% of the remaining peptides are above 6000 dalton. Partially hydrolysed formulae (pHF) have 2-18% of peptides above 6000 dalton. These larger peptides may elicit allergic reactions. pHF have a higher capacity to induce positive skin tests and provocation tests and to bind to the human serum IgE antibodies of children allergic to cow's milk. Amino acid-based formula does not have peptides so there is no likelihood of allergic reactions.

ELISA inhibition assay, with polyclonal antibodies specific for casein components of cow's milk, is a sensitive method for estimating residual antigenicity in hypoallergenic infant formulae, suggesting their potential application for quality control. Some HF are not optimal in their nutritional content. The process to reduce allergenicity may modify amino acid content or reduce its bioavailability. Changes in the absorption of calcium, zinc and copper have been found. All infant formulae promoted as 'hypoallergenic' should also be tested in milk-allergic patients to assess their allergenic potential, in addition to standard nutritional evaluation and laboratory and animal testing for antigenicity.8

Choice of formula

The choice of the substitute milk depends on its allergenicity, nutritional composition, palatability and cost. Soya milk may be safely used in many children with CMA. However, 5-30% of children with CMA are also allergic to soya protein, and some children with CMA become allergic to soya milk after its introduction. eHF have been used extensively for the treatment of children with CMA and are generally well tolerated, although there are several reports of allergic reactions, including anaphylaxis. pHF are more palatable but, because of their higher allergenicity, they are not generally recommended for the treatment of CMA.

It is recommended that children with CMA should be skin tested with eHF before this is prescribed. A negative reaction indicates eHF is safe to use. Children with a positive skin test result to the eHF should be further evaluated by an open challenge in a hospital setting where facilities for resuscitation are available.

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