UK advice in 1994 to pregnant women with a family history of allergies was to delay introduction of weaning foods that are commonly associated with allergy eg egg, nuts. This advice withdrawn in 2008, on the basis that it was unscientific and in fact there is evidence that the opposite is true. Early weaning (ie before 4 months of age) probably increases risk of eczema. Michael Perkin's EAT study has randomized 1300 unselected exclusively breast fed infants to receive early weaning with milk/egg/cod/sesame/peanut/wheat, we eagerly await the results.
Gideon Lack at Evangelina hospital in London did LEAP study LEAP (Learning about Peanut Allergy) study, randomized infants with severe eczema and/or egg allergy to receive either no peanut until age 3yr, else an age-appropriate peanut snack (Bamba or smooth peanut butter, 6g) three times a week. Among the 530 infants in the intention-to-treat population who initially had negative results on the skin-prick test, the prevalence of peanut allergy at 60 months of age was 13.7% in the avoidance group and 1.9% in the consumption group (86% reduction, P<0.001). NEJM 2015; DOI: 10.1056/NEJMoa1414850 So far, nowhere in the UK is offering this king of treatment on the NHS.
A good UK study did not find any association between antenatal and postnatal maternal diet and peanut allergy. But in the small print, there was one risk factor identified, which was total household peanut intake. This might suggest that traces of peanut in the home environment might be part of the problem (and other studies have found traces of peanut throughout homes where peanuts are eaten - must be sticky!). (Fox, J Allergy Clin Immunol. 2009 Feb;123(2):417-23).
There have been some big new studies:
- 10 000 mums in US, not high risk - eating peanuts or tree nuts ≥5 times vs less than 1 time per month in their peripregnancy diet reduced risk of allergy by 2/3: odds ratio = 0.31; 95% CI, 0.13-0.75). [Lindsay Frazier,JAMA Pediatr. 2014;168(2):156-162. doi:10.1001/jamapediatrics.2013.4139]
- 60 000 mums in Danish National Birth Cohort, those eating peanuts and tree nuts at least once weekly had kids with less asthma (OR 0.66), tree nuts also appeared to protect against rhinitis.
- 1200 US mums (not high risk) - higher maternal peanut intake during the first trimester was associated with 47% reduced odds of peanut allergic reaction (odds ratio [OR], 0.53; 95% CI, 0.30-0.94).
So it looks like eating peanut and other nuts at least once a week is a good thing! But these studies do not look at families where peanut or other allergies are already a problem (“high risk”), where things may be different.
And make sure you wash your hands and wipe down surfaces after that peanut butter wholemeal sandwich!
Preventing Allergy - Breast Feed? Which Formula?
Breast feeding seems to reduce wheezing in infancy, possibly eczema, not very clear that it prevents allergy otherwise. This kind of research is difficult because you can’t force mums to breast feed or not breast feed, so you can’t get groups that you can compare easily!
If you can't breast feed, European Academy of Allergology and Clinical Immunology (EAACI) recommends for infants at increased risk of allergic disease (defined as at least one first-degree relative affected), an extensively hydrolysed rather than normal formula should be used for the first 4 months of life. In the UK, this is not accepted practice. There is some evidence that it may prevent eczema in first few years of life. There are partially hydrolysed formulas that are less expensive (and less disgusting) but there is even less evidence that these have any effect.