Gradual exposure to peanut may put an end to peanut allergy, if results of a small study from Cambridge are followed by similar positive results.
Scientists from Addenbrooke’s Hospital in Cambridge exposed four peanut-allergic children to gradually increasing quantities of peanut protein, and found that all the children can now tolerate about 800 mg grams of protein, which is the equivalent to five peanuts, per day.
Dr Andy Clark and his co-workers report their results of their study in the journal Allergy.
Although the study is small, the implications could essentially be huge. Peanut allergies are rising in humans, with an estimated 2.5 million people in Europe and the US now vulnerable to the food allergy.
There is no current cure for food allergy and vigilance by an allergic individual is the only way to prevent a reaction but a peanut allergy can be so severe that only very tiny amounts can be enough to trigger a response.
Current recommendations in many countries, such as the UK and the US, for would-be mothers are to avoid peanuts during pregnancy, breastfeeding, and infancy.
With peanut allergy potentially fatal for some people, food manufacturers are already bound by certain regulations, depending on the country, to highlight possible allergens in a food product, such as the EU’s Labelling Directive 2000/13/EC.
Four children give hope
Dr Clark and his co-workers recruited the four children aged 12, 13, 9, and 13, and investigated if peanut oral immunotherapy (OIT) could induce clinical tolerance to peanut protein.
An initial challenge confirmed the presence of peanut allergy in the children, with one of them experiencing anaphylaxis that required an injection of adrenaline. These initial tests revealed dose thresholds ranging from five to 50 mg, which is the equivalent to between 0.025 and 0.25 of a peanut.
The children then began OIT as daily doses of peanut flour. The doses increased fortnightly from 5 to 800 mg of protein. Six weeks later, the oral challenge was repeated, and the new dose threshold values calculated. At the same time, subjects continued daily treatment.
During the post intervention challenges, the four children were found to tolerate at least 10 whole peanuts, or 2.4 grams of protein, said the researchers. This equated to a dose threshold increase of 48-, 49-, 55- and 478-fold for the four subjects.
“Each subject is currently tolerating approximately 800 mg protein (five peanuts) per day, and can tolerate at least double that amount on oral challenge,” wrote Clark and his co-workers.
“Tolerance may be lost if subjects were to stop OIT at this stage, and it is likely that long-term maintenance is required, as for other forms of immunotherapy.
“Follow-up studies are therefore required to examine the duration and frequency of maintenance therapy required to induce long-term tolerance,” they concluded.
Early exposure may be vital
A recent study comparing incidence of peanut allergy in Jewish children in the UK and Israel (where no recommendations for peanut avoidance exist) showed that children in the UK were 10 times more likely to suffer from peanut allergy than their Israeli counterparts.
Findings in the Journal of Allergy and Clinical Immunology showed that 69 per cent of Israeli children were consuming peanut, while only ten per cent of the children in the UK were eating peanuts.
Published online ahead of print, doi: 10.1111/j.1398-9995.2009.01982.x
"Successful oral tolerance induction in severe peanut allergy"
Authors: A. T. Clark, S. Islam, Y. King, J. Deighton, K. Anagnostou, P. W. Ewan