Food allergy usually shows itself in childhood, and the most common problem is a reaction to cow’s milk among babies and young children. Babies who are bottle-fed are obviously at greater risk of developing a sensitivity to cow’s milk, but atopic babies who are breast-fed can react badly to foods that the mother is eating, because minute quantities get into the breast milk. Again, cow’s milk is a common problem, but it is certainly not the only one – any food that the mother eats may act as an allergen for the breast-fed baby, especially if eaten in large quantities.
Babies may react immediately to their allergen, with symptoms such as vomiting, urticaria, and swelling of the lips, face and eyes. In such cases there is usually a positive skin-prick test. Once the allergen has been identified it must be avoided, for a while at least (see p218). Some babies grow out of the allergic reaction in time.
Not all babies react to their allergen immediately. Some have a delayed reaction with symptoms such as eczema, diarrhoea, asthma or rhinitis. Irritability, restlessness and crying are also reported, although most doctors would not accept these as allergic symptoms. Infants with delayed symptoms often fail to give a positive skin-prick test, and the link with food may not be at all obvious, either to the mother or the doctor.
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