There are about 3 million people in the United States living with peanut or tree nut allergies — and the prevalence of peanut allergies are on the rise, increasing threefold between 1997 and 2010.
In 2000, the American Academy of Pediatrics recommended that kids at high risk of peanut allergies (those with a family history, eczema or other food allergies) should not be exposed to peanut protein until they were three years old.
However, this recommendation did not stem the tide and was given up in 2008. In fact, a recent study showed that exposing high risk children to peanuts between the ages of 4 and 11 months actually lowered the risk of developing the allergy.
This rise is being seen in western countries, but not necessarily in all parts of the world. One reason for this might be the way that we prepare peanuts in the United States, which is predominantly through dry roasting.
In China, where peanut allergies are not as common, peanuts are primarily boiled or fried. It turns out that boiling or frying actually reduces the allerginicity of peanuts, while roasting increases it. (Important to note: If you have a peanut allergy, it is not safe to consume a peanut in any of these forms.)
So even though the proteins in peanuts are highly allergenic, lots of people have no reaction to peanuts at all. Why?
Scientists don't know exactly yet, but they do know it's partially genetic. But if allergies were simply hereditary, that wouldn't explain the increased prevalence.
"In humans if there were changes in genes that occurred, that would take hundreds of years to translate to disease," said Dr. Saira Sheikh.
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So that means the environment is also part of the cause.
One theory about our changing environment is the hygiene hypothesis, which suggests our immune systems need to come into contact with germs when we're young in order to respond appropriately later in life.
Our cleaner, more hygienic lifestyles mean that we're not exposed to as many viruses, bacteria and parasites as in the past.
"Perhaps because of this the immune system has shifted away from fighting infection to developing more allergies," said Sheikh, who is an allergist and immunologist at the University of North Carolina. "But this is only one theory. The truth is we still don't know the exact cause."
Even though the exact trigger of peanut allergies is unknown, new therapies are in clinical trials right now. Allergy shots for environmental allergens (pollen, mold, dust, etc.) are common but similar treatments for food allergies have not been tested until relatively recently.
The new therapies being developed are similar to allergy shots — by starting with exposure to a microscopically small amount of the allergen and then slowly increasing the amount over time, the immune system can be retrained to tolerate it.
There are a few different ways of delivering peanut protein currently being studied. One is oral, which uses a specific powder that contains a regulated (but microscopic) amount of peanut protein. There is also sublingual therapy, which uses small drops of liquid under the tongue, and epicutaneous therapy, which delivers the protein through a patch on the skin.
Sheikh said it will still be a few years before any of these are widely available, but that it's "a lot of progress from where we've come."
"Brains On" is a science podcast for kids and curious adults produced by MPR News and Southern California Public Radio.
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