One of the most common questions that I get asked in clinic is “what can we do to reduce the risk of food allergies developing?”. This is particularly common amongst mothers who already have one child with food allergy and are very keen to reduce the risk of this happening again with their next. It is worth mentioning that the tendency to have allergies in the first place is inherited. This tendency is referred to as “atopy” and children who receive atopic genes from their parents are more likely to get eczema, asthma and hay fever. The worse the eczema is and the earlier it starts, the more likely they are to get food allergies. What we don’t see is specific food allergies passed on from generation to generation, so having a parent with a particular allergy such as kiwi or peanut doesn’t seem to increase the risk of that particular allergy in the child. However, having an allergic parent in itself does increase the risk of the child getting allergy problems.
The first piece of advice I would always give is to ideally try to breastfeed for 4-6 months because, as well as the numerous other benefits that this provides, there is evidence that this helps limit the likelihood of allergies developing. There has been a lot of interest over time in other possible approaches to reduce the likelihood of food allergy. There remains a lot of interest in probiotics (friendly bacteria). For example, mums taking probiotics during pregnancy, where there is a strong family history of eczema, has been shown to reduce the risk of eczema in infants although beyond this the results have generally been a little disappointing until more recently. Emerging research is now showing the adding probiotics to the infant formulas given to babies with milk allergy may help them outgrow their allergy quicker and reduce the risk of them developing other allergies over time.
Something else that research has shown us is that avoiding particular foods during pregnancy or indeed during breastfeeding doesn’t seem to make any difference and it is therefore not necessary for mums to try and do this. Likewise, there does not seem to be any particular benefit of eating large amounts of any particular foods such as nuts as this again doesn’t seem to impact the likelihood of the child getting a nut allergy.
More recently, there has been a lot of interest in early introduction of allergenic foods such as peanut as a strategy for preventing peanut allergy. This came from the observation that children who have peanut introduced very early into the infant weaning diet seem to be protected from peanut allergy even if they have eczema. The most important evidence, however, comes from the LEAP Study which was carried out at St Thomas’ Hospital. This involved over 600 babies, all of whom were considered to have a very high risk of peanut allergy because of either pre-existing egg allergy or the presence of significant eczema. They were recruited into the study between 4-11 months of age and were randomly selected either to completely avoid peanut in their diet (which was the advice from the Department of Health at the time, but has since been withdrawn) or to have peanut deliberately introduced into their diet on a regular basis, 3 times a week. After a 5-year period of observation, the number of children developing peanut allergy is each group was observed. The results were remarkable, with a highly significant reduction in the amount of peanut allergy in the children who deliberately introduced peanut into their diet and kept it in there. This included children who, when they entered into the study, already had a positive allergy test to peanut even though of course they were not allergic yet.
This has led to further research and also changing guidance in the United States where they now recommend that in children who have eczema or egg allergy at around 4-6 months of age, they have an allergy test to help inform the decision as to whether peanut should be introduced. If the test is negative then peanut can be safely introduced at home. However, if the test is slightly raised, peanut should still be introduced but this should be done carefully under medical supervision. The idea here is that if children who are on their way to becoming allergic can successfully get peanuts regularly into their diet, and as a result be preventing the allergy from happening. My own practice is very much along these lines and in infants who I see with eczema, I am very keen to do allergy tests so that where at all possible, we can introduce allergenic foods into the early weaning diet and reduce the risks of allergies developing in the first place. Further research has shown that the principle seems to hold for egg and sesame and possibly other foods as well.
So in summary, where there is an increased risk of food allergy, particularly in infants with eczema, then it is worth considering allergy testing and carefully consider decisions about food introductions. This should ideally be done alongside exclusive breastfeeding for 4-6months where possible but there is no need for mum to avoid any particular foods during pregnancy or breastfeeding.