There is evidence that allergens can be transmitted via breast milk. However, allergens are usually transmitted in a highly processed form which is tolerated well by the vast majority of infants. Occasionally, exclusively breast fed babies can present with signs of allergies, rarely immediate type IgE-mediated manifestations, and more commonly delayed type manifestations of the gut. Such delayed manifestations may include an “allergic proctocolitis,” presenting with blood and mucous in the stool of an otherwise well baby, or an “enteropathy” or “colitis,” in which symptoms may include diarrhoea, blood in the stools, failure to thrive, crampy colicky pains or upper gastrointestinal symptoms such as troublesome reflux.
Blanket elimination of foods during breastfeeding is discouraged and potentially harmful to both mother and infant. If there is a suspicion of food allergy presenting during breast feeding, an assessment by a specialist to determine the exact causative allergens is encouraged. The vast majority of infants who present with allergies during the breastfeeding period can continue to breastfeed with targeted dietary exclusions by the mother.
If the child is found to have an IgE mediated food allergy, they can occasionally present with symptoms during breastfeeding, most commonly rashes shortly after a feed, usually a few hours after the mother has eaten the “responsible” food. However, many children with immediate type allergies do not react when the mother has eaten the food, as the food is so “processed” by the time it gets into the breast milk. In such cases, the mother need not eliminate the food from her diet, but of course the infant needs to avoid the food during the weaning process.
Allergens transmitted via breast milk can occasionally worsen eczema. Certainly, there is no role for blanket elimination diets in the breastfeeding mother if the child has eczema. Targeted avoidance should be advised by the specialist after appropriate assessment. Many
children with eczema have positive allergy tests but will tolerate the food they’ve tested positive to, hence this is best dealt with by an allergist with the capacity to perform food challenges if needed. Generally, if foods seem to be tolerated with no obvious immediate symptoms, and eczema is treatment responsive, then foods do not need to be eliminated regardless of allergy test results.
Cow’s milk is the most common trigger for early manifestations of food allergy in breast fed babies, regardless of clinical presentation. Strict avoidance of cow’s milk from the mother’s and infant’s diet is needed in cow’s milk protein allergy, unless otherwise suggested on the basis of allergy testing. 95% of cow’s milk allergic infants will respond to strict maternal elimination, and can thus continue to breast feed. In allergic proctocolitis, the response to maternal elimination occurs within 48-72 hours. In enteropathy, the response may take 2-3 weeks, hence the trial of maternal elimination needs to be longer to look for improvement in symptoms. Very occasionally (in 5% or fewer of cases), symptoms will persist despite strict maternal elimination. In such cases, the infant may actually be reacting to breast milk proteins that are “cross reacting” (“confused” by the body) with cow’s milk protein. This latter case is rare, but will necessitate discontinuation of breastfeeding and use of an amino acid formula.
In all cases of maternal dietary elimination, a dietitian should be involved to help identify hidden sources of milk protein (or other identified allergens) in the diet, and to ensure nutritional adequacy of the maternal diet. A good pre-natal vitamin and a calcium supplement (1000 mg calcium daily) are recommended for the breast feeding mother if she is eliminating dairy from her diet.
In conclusion, allergies can appear in exclusively breast fed babies. Breastmilk is a precious and immuno-protective resource, and allergies in the breast feeding child are not a reason to stop breast feeding. Determination of the exact allergies is essential; blanket elimination of allergenic foods from the mother’s diet is not advised. The vast majority of infants who present with allergies during the breastfeeding period can continue to breastfeed with targeted dietary exclusions by the mother.