Peanut allergy is one of the most common food allergies, affecting of people living in the west. And, for many years, their .
But a out of the US shows that the rate of peanut allergy diagnoses in infants has actually declined. It appears this decline may be due to changes in allergy guidelines 鈥� highlighting the importance of introducing this common allergen early on.
A food allergy is a type of allergic reaction which occurs when your immune system reacts inappropriately to things it should ignore 鈥� such as pollen or certain types of foods. The most common allergic condition is 鈥� a reaction to pollen. is one of the most common true food allergies 鈥� and also the most common cause of fatal food reactions.
The proportion of people with food allergies in England has between 2008 and 2018. Similar data in the US showed more than developed a food allergy between 1997 and 2008.
The reasons for these increases are complex and due to many factors 鈥� including exposure to , alterations in the and . There also appears to be a link between certain inflammatory health conditions (such as and an infant鈥檚 likelihood of developing a food allergy.
But this latest study has shown that the US appears to have deviated from this overall trend, with peanut allergies actually falling in infants.
The study examined changes in the rates of peanut allergies since 2015. This was the year in the US changed to encourage infants considered most at risk of food allergy (such as those with atopic dermatitis) to be introduced to peanuts early in life.
had shown that these guideline changes had resulted in an increase in the number of parents introducing peanuts into their child鈥檚 diet by one year of age. The research team wanted to assess whether this had had any affect on peanut allergy rates, too.
They enrolled almost 39,000 children during the pre-guidelines phase (when advice was to avoid peanuts) and around 47,000 in the post-guidelines phase (after 2015). Allergy incidence in both groups was tracked for one to two years.
Early exposure to peanuts is linked with reduced likelihood of developing an allergy.
The research showed that the total rate of peanut allergy decreased from almost 0.8% to 0.5%. This meant fewer at-risk infants developed a peanut allergy following the guideline change.
These findings mirror prior work in the UK showing that before the age of five was linked to a of developing an allergy.
Food allergy guidelines
In the late-1990s and early 2000s, the burgeoning incidence of food allergies and their life-threatening implications prompted sweeping policy changes in many western countries.
In and , guidelines changed to recommend high-risk allergens (such as peanuts) were completely avoided by pregnant women, breastfeeding mothers and infants considered at high risk for allergy.
But these guidelines were made in the absence of any rigorous studies actually showing they鈥檇 have a positive effect. Indeed, had suggested there may be no benefits 鈥� showing that eating potential allergens early in life actually invokes an important phenomenon called .
Oral tolerance is where the immune system ignores a potential allergen after it has been introduced to the gut through diet. How oral tolerance develops isn鈥檛 fully understood, but involves several mechanisms that help immune cells to be effectively so they don鈥檛 mistake certain foods for a threat.
But despite the change in advice to avoid peanuts, rates of did not fall.
A conducted in 2008 consequently showed there was no clear evidence that eating or not eating peanuts (or foods containing peanuts) during pregnancy, while breastfeeding or in early childhood had any effect on the chances of a child developing a peanut allergy. As such, the advice in the UK to avoid peanuts (and eggs) during pregnancy and early childhood was .
A randomised trial conducted since this policy change came into place showed that among infants considered at high risk of allergy, consistent consumption of peanuts from 11 months of age resulted in an over of peanut allergy by the age of five compared with children who had avoided peanuts.
Other studies , which subsequently led to guidelines in 2015.
Many questions remain
It鈥檚 now increasingly clear that the early introduction of potentially allergic foods may actually benefit us and reduce our risk of developing a life-changing allergy. Nonetheless, there鈥檚 much we still don鈥檛 understand.
For example, while the mechanisms underpinning oral tolerance are being elucidated, we still don鈥檛 know what the best window of age is for safely invoking it.
We also don鈥檛 understand why infants with atopic dermatitis are most at risk of developing a food allergy. The hypothesis is that early exposure to food proteins through a disrupted skin barrier is what , as the immune system becomes sensitised to the food.
It鈥檚 also important to note that overall, the incidence of food allergies is still increasing. While this recent US study offers hope for preventing some types of food allergies, questions still remain. For example, some people can develop food allergies during . More must be done to understand why this happens.
There are also still barriers impeding access to diagnosis for severe food allergies. This means many at-risk patients have not been diagnosed, so they also have been prescribed potentially . These trends are magnified for people living in more deprived areas of the country.
Much more needs to be done to answer these questions and tackle food allergies more broadly.
, Professor in Immunology,
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