May 14, 2010 -- Peanut allergies in children have more than tripled in the United States from 1997 to 2008, an alarming trend that can’t yet be explained, a new study says.
“We don’t know why this is happening, but there are many theories,” study author Scott H. Sicherer, MD, of the Jaffe Food Institute at Mount Sinai School of Medicine, tells WebMD.
His research team surveyed 5,300 households in 2008 and discovered that 1.4% of children were thought to have peanut allergies, more than three times the 0.4% rate found when a similar tally was taken in 1997.
The study says the percentage of children with allergies to peanuts or tree nuts soared to 2.1% in 2008 from 0.6% in 1997, while remaining at 1.3% for adults.
Peanut Allergy on the Rise: Why?
One theory for the rise, the hygiene hypothesis, holds that “we’ve become very good at preventing natural infections, and the immune system is not chewing on things it would normally be chewing on,” Sicherer tells WebMD. “We’re not living on farms anymore, we have lots of antibiotics, but seeing an increase means that something has changed in the environment.”
The theory suggests that “clean living” and more medication use leaves immune systems in a condition that is more prone to attack harmless proteins, such as those in foods, pollens, and animal dander.
The increase also could be related, he says, to the way peanuts are processed.
“We roast peanuts, and potentially, roasting it makes a more allergenic food out of it,” he says. “Some people theorize that the oil in peanut butter might make it more allergenic. Roasting peanuts changes the sugar and makes the protein more stable to digestion and easier for the immune system to attack.”
Peanut Allergy Rate Similar Across Globe
Researchers surveyed 5,300 households representing 13,534 people in 2008, a response rate of 42%.
The study is the first of its kind to incorporate all age groups within a national sample and to use the same methods over such an extended time period. It also is the first study in the U.S. to evaluate allergies to sesame seeds, according to the news release.
Tree nut allergies have increased from 0.2% in children in 1997 to 1.1% in 2008, the study says. Sesame allergy was reported in 0.1% of children and adults.
“Our research shows that more than 3 million Americans report peanut and or tree nut allergies, representing a significant health burden,” Sicherer says in the news release. “The data also emphasize the importance of developing better prevention and treatment strategies.”
The American Academy of Pediatrics used to instruct parents to avoid peanut use until their kids reached age 3, but that has been rescinded, Sicherer says.
The researchers say the rate of peanut allergy they found in the U.S. is similar to results from studies using different methods in the United Kingdom, Canada, and Australia.
The study is published in the May 12 issue of the Journal of Allergy and Clinical Immunology.