NEW YORK (Reuters Health) - Compared to children without peanut or tree nut allergies, kids who have both these allergies may also be more likely to develop an allergy to sesame seeds, a small study suggests.
The researchers linked a history of dual allergic reactions to peanuts and tree nuts with a 10-fold higher risk of allergy to sesame seeds - the tiny seeds that are commonly found in hummus and on hamburger buns.
The researchers also looked for a link between nut allergies and coconut allergies, but they did not find one.
More than 3 million people in the U.S. have an allergy to peanuts, tree nuts or both -- the foods also most notorious for triggering severe allergic reactions in children.
Some recent evidence has hinted that children with these allergies may be more prone to developing allergies to previously less-recognized triggers, such as sesame.
"I certainly screen my patients with peanut and tree nut allergy for sesame seed allergy," Dr. David Fleischer of National Jewish Health in Denver told Reuters Health.
Coconut has also appeared on the radar of allergists, particularly since the U.S. Food and Drug Administration (FDA) issued new labeling laws that categorize it as a tree nut.
"In reality, it is a palm fruit," added Fleischer, who was not involved in the new study but has published widely on peanut and tree nut allergies. "The FDA has confused the public."
To help sort out these relationships, Dr. Wanda Phipatanakul, of Children's Hospital Boston, and her colleagues studied the medical records of 191 children who had skin prick tests for sesame allergy and 40 who had tests for coconut allergy.
About 37 percent and 20 percent of the kids had positive test results to sesame and coconut, respectively, suggesting that their immune systems produced antibodies in reaction to the food.
When the researchers looked only at the children who had already proved sensitive to peanuts or tree nuts, between 50 percent and 60 percent showed sensitivity to sesame. Overall, they had a 6- to 10-fold higher risk of sesame sensitivity compared to children who did not have peanut or tree nut sensitivity, the researchers report in the medical journal Pediatric Allergy and Immunology.
But just because kids are "sensitized" doesn't mean they are truly allergic, Phipatanakul told Reuters Health in an e-mail.
Between 13 percent and 15 percent of peanut and tree nut allergic children were actually allergic to sesame, which turned out to be about the same proportion as among kids who didn't have the nut allergies.
The rate of sesame allergy jumped up to 50 percent for children allergic to both nuts, however.
Coconut sensitization or allergy, on the other hand, did not appear to be related to kids' reactions to peanut, tree nut or both.
"Most patients that are tree nut allergic don't really have to avoid coconut," noted Fleischer.
The findings are also consistent with earlier research connecting peanut and sesame allergies, he said.
However, both Fleischer and Phipatanakul pointed to limitations in the study, including its small size and lack of food challenges, the "gold standard" for diagnosing food allergies. They noted that more studies are needed to fully understand the relationships.
"We pretty much know that all food allergies are on the rise, particularly peanut. But this doesn't necessarily say that sesame seed allergy is an epidemic by itself," said Fleischer. "We just know it is associated with peanut, and we need to be aware that patients are at risk and should to be tested for it."
"If someone has a concern about any allergy they should always see an allergist," he added. "Any person can react to any food."
SOURCE: http://bit.ly/ffjpbh Pediatric Allergy and Immunology, December 2010.