Simple Test May Predict Whether Your Child Will Outgrow Their Peanut Allergy

Antibodies are proteins your immune system produces to recognize unwanted substances. They bind to and inactivate these intruders, or recruit immune cells to help destroy them.

People with allergies overproduce certain antibodies when exposed to an allergen, a substance their immune system has become sensitized to. These somewhat allergen-specific antibodies are good indicators of the type and severity of a person's allergy.

And yet, when it comes to childhood peanut allergies, detail on these antibodies as biomarkers is lacking.

"Little was known before this research about whether antibodies could be used as biomarkers of naturally resolving peanut allergy during the primary school years," says population health graduate student Kayla Parker, from the Murdoch Children's Research Institute.

Parker and her team searched for long-term trends among children whose peanut allergies persisted or resolved by age 10 - specifically, their levels of two types of antibodies that respond to peanuts and the main allergen in peanuts, a protein called Ara h 2.

She hopes the new research will help allergy specialists identify which children are likely to experience an ongoing peanut allergy, and who might grow out of it.

The findings are based on a much larger dataset from an ongoing longitudinal population-based study of food allergy that began in 2007, called HealthNuts.

Within this data, the researchers focused on 156 children from Melbourne, who joined the study from 2007 onwards as 12-month-old infants with confirmed peanut allergies. Over the following years, these children were given questionnaires, skin prick tests, blood tests, and oral food challenges at ages 4, 6 and 10 years.

Two-thirds of these children did not outgrow their peanut allergy by age 10, but the vast majority of those who did achieved tolerance by 6 years old.

The team found it wasn't the antibody levels in themselves that were linked to allergy persistence or resolution, but rather a change in the level of each type of antibody over time.

"We found the longitudinal changes were more useful in predicting those children on the path to peanut allergy resolution than relying on a single snapshot at one time point," Parker says.

Children whose peanut allergies persisted tended to have increased reactions in skin prick tests and increased levels of the antibodies peanut sIgE and Ara h 2 sIgE through the years.

Meanwhile, children whose peanut allergies eventually resolved followed quite a different trajectory. As the years went by, their reactions to skin prick tests subsided, along with their levels of antibody Ara h 2 sIgE, while levels of the antibodies peanut sIgG4 and Ara h 2 sIgG4 increased.

Some children with peanut allergies, it seems, experience an antibody shift during childhood, and this correlates with whether their allergy persists or resolves.

The nature of this link remains unclear, but it may help allergists identify which of their patients are likely to need ongoing review to monitor the status of their allergy, to see if it does indeed subside, and which of them are probably going to need to steer clear of peanuts long-term.

"[Children] with high or increasing levels of these biomarkers are less likely to spontaneously outgrow their peanut allergy and could be prioritized for potential early treatment options if available," Parker says.

In recent decades, many schools have totally banned the risky legume from school lunchboxes, though evidence that these blanket bans work to prevent allergic reactions is lacking. Allergy experts say these bans may also give parents and kids a false sense of security.

Research shows more effective approaches include hand-washing, discouraging food-sharing, and limiting unexpected sources of peanut exposure like certain materials for craft and science projects. Training school staff on how to respond to severe allergic reactions is also essential.

There is no routine treatment currently available for peanut allergy, so children with these allergies should strictly avoid peanuts.

However, the researchers behind this study emphasize clinical trials exploring new treatment options are available to Australian families, listed on the National Allergy Centre of Excellence's Allergy Studies Directory.

This research was published in Allergy.