Monday March 7 2016
Food allergies affect around 1 in 14 children
"The effects of eating peanut products as a baby to avoid the risk of allergy have been backed up by new research," BBC News reports. A new study suggests eating peanut snacks in the first year of life reduces the risk of a nut allergy in children.
The study reported results from 550 children who completed a trial where they were given either a peanut snack or told to avoid peanut products. During follow-up, all of the children were asked to avoid peanuts for a year.
Children who avoided peanuts as part of the trial were more likely to have a peanut allergy at six years old (18.6%) than the children who ate the peanut snack (4.8%).
The proportion of children in the peanut snack group who developed a peanut allergy was similar when they completed the trial (3.6% at age five) and a year later (4.8% at age six).
This suggests the protection built up from their exposure to peanuts was maintained, even if peanut products were avoided for a year.
These findings show promise, but it is unknown how long the effects last. Children who already have another allergy, such as eczema, or have a history of allergy in their immediate family, are at greater risk of developing a peanut allergy.
Current advice states that if your child falls into this group, you should talk to your GP before you give them peanuts for the first time.
Where did the story come from?
The study was carried out by researchers from the Guys and St Thomas' Hospital Trust, the University of Southampton, and the University of California.
Funding was provided by the National Institute of Allergy and Infectious Diseases of the National Institutes of Health, Food Allergy Research and Education, the Medical Research Council and Asthma UK Centre, and the UK Department of Health.
The clinical trials unit was supported by the National Peanut Board, and the Food Standards Agency provided some funding for taking blood samples.
The study was published in the peer-reviewed New England Journal of Medicine on an open access basis, so you can read it for free online.
The study has been reported accurately by the BBC, who warned that further studies are needed to see if the effect lasts longer than the 12 months tested in this study.
What kind of research was this?
This was a follow-up study of a randomised controlled trial testing the effect of giving products containing peanuts to children who are at a high risk of allergy in early life. The original results of this trial were reported by Behind the Headlines in February 2015.
This study aimed to investigate whether the rate of peanut allergy stayed low in the group who ate peanut products, compared with those who had not. The aim was to see if results corresponded to the original trial, even after the peanut group stopped eating peanut products.
What did the research involve?
This study followed up children at high risk of allergy who had completed a previous UK-based randomised controlled trial.
The children were under a year old when the trial started, and were at high risk of peanut allergy because they had severe eczema or egg allergy, or both.
They were tested before the start of the trial to make sure they did not already have a peanut allergy.
The children were randomly assigned to either avoid peanuts or eat peanuts in the form of a smooth peanut mixture until the age of five, at which time they were tested for peanut allergy.
During this follow-up study, the researchers asked all the children to avoid peanuts for 12 months, after which time they tested the children who had not shown signs of peanut allergy before to see if they had developed a peanut allergy.
This was done by giving them a small amount of peanut protein while they were closely observed by the researchers to see if they showed any signs of an allergic reaction.
Researchers measured to what extent the children had avoided peanuts using a questionnaire that assessed how often they ate various foods, including peanuts and products that contained peanuts. Parents regularly filled this questionnaire out.
The researchers also took dust samples from children's beds, which were measured for peanut protein levels and used as an independent sign of peanut consumption.
The researchers performed two separate analyses of the participants:
- The first looked at all participants in the follow-up study who were tested for a peanut allergy outcome, regardless of whether they had successfully avoided peanuts or not (intention to treat).
- The second looked at all participants who successfully avoided peanuts for 12 months (per protocol analysis).
Avoidance was judged to be sufficiently successful if all three of the following criteria were met during the year:
- The child ate 2g or less of peanut on no more than six occasions.
- The child ate 1g of peanut or less on no more than 12 occasions.
- The child ate no more than 18g of peanut in total.
What were the basic results?
The researchers included 550 participants for whom they had complete data.
The intention to treat analysis found the proportion of children with peanut allergy at the age of six was significantly higher in the peanut avoidance group (18.6%) than the consumption group (4.8%).
Although the proportion of children in the trial's peanut-consuming group who had peanut allergy increased slightly between the end of the original trial (when 3.6% had peanut allergy) and the end of the follow-up year (when 4.8% had peanut allergy), this difference was not large enough to say that it had not occurred by chance.
It therefore wasn't deemed statistically significant. This means the early exposure to peanuts still appeared to be protecting the children from developing an allergy.
Similar findings were seen for the 445 children (80%) who adequately stuck to avoiding peanuts.
How did the researchers interpret the results?
The researchers concluded that, "Among children at high risk for allergy in whom peanuts had been introduced in the first year of life and continued until five years of age, a 12-month period of peanut avoidance was not associated with an increase in the prevalence of peanut allergy. Longer term effects are not known."
This was a follow-up study of a well-designed randomised controlled trial. The original study found the early introduction of regular small amounts of peanut protein to infants at high risk of having peanut allergy reduced the proportion that developed a peanut allergy by the age of five, compared with avoiding peanuts completely.
The latest study found that even if the children who had been exposed to peanuts then avoided them for 12 months, this did not significantly increase their likelihood of developing a peanut allergy.
Strengths of the study include the use of objective tests to determine how well the children managed to avoid peanuts, as well as a questionnaire.
The group who avoided peanuts during the trial were better at avoiding them during follow-up, and this may affect the findings for the overall comparison. However, the researchers got similar results if they only looked at the children who adequately avoided peanuts.
The study has shown that the protection built up from the initial early exposure can be sustained, even if peanut products are avoided for a year. How long these effects would last beyond this time is not known.
While these findings show promise for children at high risk of peanut allergy, it is not advisable to try this if you think your child is likely to develop a peanut allergy. The children trialled were closely monitored by researchers to ensure they were safe.
Children who already have another allergy, such as eczema or a diagnosed food allergy, or have a history of allergy in their immediate family, such as asthma, eczema or hay fever, are at greater risk of developing a peanut allergy.
If your child falls into this group, you should talk to your GP or health visitor before you give them peanuts or food containing peanuts for the first time.
Warning signs of a severe allergic reaction (anaphylaxis) include:
- itchy skin or a raised, red skin rash
- swollen eyes, lips, hands and feet
- feeling lightheaded or faint
- swelling of the mouth, throat or tongue, which can cause breathing and swallowing difficulties
- abdominal pain, nausea and vomiting
- collapse and unconsciousness
If you suspect anaphylaxis, dial 999 immediately.