Tuesday February 24 2015
Under 5s should not have whole peanuts
"The cure for peanut allergy – peanuts, from the age of four months," says The Guardian.
This is dangerous headline advice, potentially leading parents to think they can simply give peanuts to an allergic child and cure them. This is irresponsible. Parents are also advised not to give peanuts – or any whole nuts – to children under the age of five, because of the risk of choking.
There are ongoing trials to assess whether medically supervised gradual introduction to peanut protein can help children with a peanut allergy – but the study on which the headline is based did not do this. It looked at whether foods containing peanuts, such as peanut butter, may play a role in helping to reduce the risk of children developing a peanut allergy.
The news is based on a well-designed trial in 640 infants aged between four and 11 months, who were not already allergic to peanuts, but were at increased risk of developing allergies due to having other food allergies or eczema. It compared the effects of giving the infants regular small amounts of peanut protein (in the form of smooth peanut butter or snacks containing peanut butter) or avoiding peanuts altogether up to the age of five.
It found that early introduction of peanut products (not whole nuts) reduced the proportion that developed a peanut allergy by age five, compared to those avoiding peanuts completely.
It is important to know that this study was not about treating infants or children who already have a peanut allergy. All children had a skin prick test before starting the trial, and those who showed an allergic reaction to peanut protein were excluded. Those who developed an allergic reaction stopped eating the products.
If your child shows signs of a peanut allergy, you should not try to feed them peanuts, and should instead consult your GP.
Where did the story come from?
The study was carried out by researchers from King’s College London, Guy’s and St Thomas' National Health Service Foundation Trust, and other research centres in the UK and US. It was funded by the US National Institute of Allergy and Infectious Diseases, Food Allergy Research and Education, the UK Medical Research Council, Asthma UK, the UK National Institute for Health Research, the US National Peanut Board and the UK Food Standards Agency.
The study was published in the peer-reviewed New England Journal of Medicine, and has been made open access, so is available for free online.
Other than the Guardian’s print and The Daily Telegraph's headlines (both referring to "peanuts" rather than peanut products), the media generally reported on this study well. It’s worth noting that the headline slips might be due to a King's College London press release entitled "Eating peanut at an early age prevents peanut allergy in high-risk infants", which is not as clear as it could be.
Other sources avoided saying that the infants were fed "peanuts" in their headlines. For example, the Mail Online avoided a sensationalist headline and gave sensible warnings to parents not to try this at home.
What kind of research was this?
This was a randomised controlled trial (called the Learning Early about Peanut Allergy (LEAP) trial) looking at whether introducing children to peanuts at an early age could reduce the risk of them developing a peanut allergy.
Peanut allergy in children is reported to have doubled in westernised countries in the past decade, with between one in 100 and three in 100 children being affected. Peanut allergy is the most common cause of anaphylactic shock and death due to food allergy.
UK and US guidelines have in the past recommended pregnant and breastfeeding women and infants at high risk of allergy to avoid "allergenic" foods such as peanuts. However, this was not shown to reduce the likelihood of developing food allergies, so this recommendation was withdrawn.
It is still not clear whether avoiding or introducing allergenic foods early on is a better way to avoid food allergies later in life. Researchers in the current study wanted to compare these strategies to find out which might be better for reducing the chance of developing a peanut allergy.
A randomised controlled trial is the best way of comparing different interventions or approaches. Assigning people randomly should ensure that the groups are well balanced, and therefore any differences between the groups should be due to the different interventions.
What did the research involve?
The researchers enrolled infants aged between four and 11 months of age with severe eczema, egg allergy, or both, and randomly assigned them to either peanut exposure or peanut avoidance.
Infants in the exposure group who did not show signs of a peanut allergy were given at least six grams (g) of peanut protein a week up to the age of 60 months. Infants in the avoidance group were not given any peanut products. The researchers tested the children during the trial to see if any of them developed a peanut allergy.
Crucially, before starting the trial, they tested the infants using a skin prick test, using peanut protein to identify those who showed signs of an allergic reaction with a wheal (a small raised area of the skin). Those who developed a large wheal (area of raised or reddened skin) at the site of exposure (more than 4mm in diameter), as this is a strong sign of an allergic reaction, were excluded from the study. Those showing a slight reaction (wheals of up to 4mm) were included, but analysed separately to those showing no skin reaction.
Those who had been allocated to the peanut exposure group then had a further "food challenge" test to see if they reacted to eating a small amount of peanut protein (2 to 3.9g). Those who showed a slight reaction to peanuts in the skin prick test were instructed to avoid them, but still analysed as part of the "peanut exposed" group. This was to make sure the groups stayed balanced.
The peanut protein used in the study was a commercially available snack made from peanut butter and puffed maize, called Bamba, or smooth peanut butter (Duerr’s or Sunpat brands) if the infant did not like the snack. The researchers assessed how well the families stuck to the assigned diet for the infants with a standard food questionnaire.
The researchers had telephone calls with the parents every week until the infants were 12 months old, then every fortnight up to the age of 30 months, then monthly. They assessed the infants face-to-face at ages 12, 30 and 60 months, and in any cases where the infant showed signs of a possible peanut allergy. At these visits, they again assessed whether the child showed signs of being allergic to peanuts. This started with a skin prick test with peanut protein.
Those who reacted to the skin prick test, had shown any signs of allergic reaction to peanut protein, sesame or tree nuts, or had an anaphylactic reaction to any food during the study, were given gradually increasing amounts of peanut protein, while being closely observed for any reaction. If they showed a reaction, the test was stopped.
The researchers doing this test did not know which group each infant had been part of. All other children were given 5g of peanut protein and also observed for any reaction. Eleven children who had inconclusive results on the food challenge tests, or who missed the test, were assessed based on their medical history, skin prick test and level of peanut allergy-related antibodies in their blood.
The researchers then compared what proportion of children in each group had developed a peanut allergy, to see if it differed. They looked at children who showed a positive skin prick test at the start of the study and those who showed a negative skin prick test separately.
What were the basic results?
Overall, 628 out of the 640 infants recruited (98%) provided enough information for their data to be analysed.
Among the 530 children who were negative on the first skin prick test, 13.7% of those who avoided peanuts had developed a peanut allergy by 60 months, compared to only 1.9% of the peanut exposed group.
Among the 98 children who were positive on the first skin prick test, 35.3% of those who avoided peanuts had developed a peanut allergy by 60 months, compared to 10.6% of the peanut exposed group.
These results were statistically significant, meaning that they were unlikely to have occurred by chance. Similar results were obtained even in a "worst case scenario", where all participants in the peanut exposure group with missing data were assumed to be allergic, and the opposite assumed for the peanut avoidance group.
There were no deaths among the infants in the study, and there was no difference between the groups in serious adverse events or need for hospitalisation. There were more adverse events overall in the peanut exposed group. The events that were more common in the peanut exposed groups included upper respiratory tract infection, viral skin infection, gastroenteritis, urticaria (hives – a raised, itchy rash), and conjunctivitis. These events were generally mild to moderate in severity for both groups.
How did the researchers interpret the results?
The researchers concluded that, "the early introduction of peanuts significantly decreased the frequency of the development of peanut allergy among children at high risk for this allergy".
They say that this, “raises questions about the usefulness of deliberate avoidance of peanuts as a strategy to prevent allergy”.
This well-designed randomised controlled trial has found that the early introduction of regular small amounts of peanut protein to infants at high risk of having allergies reduced the proportion who developed a peanut allergy by age five, compared to avoiding peanuts completely.
The study looked at a group of infants who were at a particularly high risk of going on to develop food allergies, because they already had severe eczema or an allergy to eggs, or both.
It is important to know that this study was not about treating infants or children who already had a peanut allergy. Those who showed a strong reaction on a skin prick test were excluded from the study, and those who showed an allergic reaction to eating peanut protein during the study were advised not to eat them. The results of this study do not apply to this group, and the researchers say they don’t know if their approach would work and be safe in this group.
The main limitation to the study was that parents and children could not be blinded to which group they were part of. However, the use of objective tests for allergic reactions should mean that their views cannot influence this outcome. There appeared to be a high level of compliance with the group allocations, but this was largely based on reports from the parents, so may not be fully accurate.
Overall, this study suggests that eating peanut products early in life may reduce the risk of children with a tendency towards allergies developing a peanut allergy up to age five. The researchers now plan to follow the participants for longer to see if the effects are maintained over time, even if they stop eating peanut products. As a number of experts point out in the media, this is not yet at a stage where it could be recommended to families to try at home.
If your child shows signs of a peanut allergy, do not try to feed them peanuts, and instead consult your GP.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.