In a previous study, the authors of this paper found that Jewish children in the UK had 10 times the rate of peanut allergy as Jewish children in Israel. This also correlated with the earlier introduction of peanuts in Israel due to a tasty snack called Bamba.
Following the discovery of these results, the hypothesis was that the early introduction of peanuts led to a reduced rate of peanut allergy. And so the LEAP study (Learning Early About Peanut allergy), that you’ve been reading about all over the media this week, was born.
The study included patients aged 4-11 months with severe eczema and/or egg allergy seen at one site in the UK over a three year period.
There were 640 participants.
Patients had a skin test at the beginning of the study and were split into those who had a positive reaction and those who didn’t.
Each of these groups was then split into those who would eat peanuts and those who would not.
You may be thinking: “they gave peanuts to infants with a positive skin test”?!…and you would be right. But those with a positive skin test had incremental doses of peanuts, as opposed to those with a negative skin test who had the full 2g dose of peanuts up-front.
If they had a reaction to the first peanut challenge, then they were excluded from the study.
Those in the peanut challenge group had at least 6g of peanuts (Bamba or peanut butter) each week until 60 months of age. Those in the non-peanut group avoided peanuts until 60 months of age.
Adherence was 92%.
Patients were reviewed regularly over the 5 year period.
The primary outcome was peanut allergy at 60 months of age which was diagnosed via an oral food challenge. This was assessed by measuring wheals, and also by measuring peanut-specific IgG4:IgE ratio
At 60 months of age, 13.7% of the avoidance group and 1.9% of the consumption group were allergic to peanuts (86.1% relative reduction in the prevalence of peanut allergy).
For those who had a positive baseline skin-prick result, at 60 months of age, 35.3% of the avoidance group and 10.6% of the consumption group were allergic to peanuts (a 70.0% relative reduction in the prevalence of peanut allergy).
This was assessed using a validated food-frequency questionnaire which confirmed that those in the consumption group were having 7.7g of peanuts per week versus 0g in the avoidance group. Also, bed dust particles were analysed for peanuts and there was significantly more in the consumption group.
99% of participants in both groups reported at least one event. There were no deaths. Interestingly there were more episodes of anaphylaxis in the avoidance group than in the consumption group.
Although all adverse events were mild, the consumption group had more upper respiratory tract infection, viral skin infection, gastroenteritis, urticaria, and conjunctivitis.
The results seem fairly conclusive – peanut consumption was associated with an 86% reduction in peanut allergy at 60 months of age (among participants who had had negative results on a peanut-based skin-prick test at study entry); and there was a 70% reduction among those who had had positive test results at study entry.
It’s not known what will happen to these patients in the future. Do they need to continue with peanut consumption to avoid developing an allergy, or can they just stop consuming peanuts?
That’s where LEAP-On (Persistence of Oral Tolerance to Peanut) comes in. Watch this space…