Not surprisingly, researchers also found targets of bullying were more distressed and anxious and had a worse quality of life, in general, than those who weren't picked on.

Bullying has become a concern among parents, doctors and school administrators since research and news stories emerged linking bullying - including online "cyberbullying" - with depression and even suicide.

"There has been a shift and people are more and more recognizing that bullying has real consequences, it's not just something to be making jokes about," said Dr. Mark Schuster, chief of general pediatrics at Boston Children's Hospital and a professor at Harvard Medical School, who wrote a commentary published with the new research.

Studies suggest between one in ten and one in three of all kids and teens are bullied - but those figures may vary by location and demographics, researchers noted.

The new findings come from two studies published Monday in the journal Pediatrics.

In one, Dr. Eyal Shemesh from the Mount Sinai Medical Center in New York and his colleagues surveyed 251 kids who were seen at an allergy clinic and their parents. The children were all between age eight and 17 with a diagnosed food allergy.

Just over 45 percent of them said they'd been bullied or harassed for any reason, and 32 percent reported being bullied because of their allergy in particular.

"Our finding is entirely consistently with what you find with children with a disability," Shemesh told Reuters Health.

A food allergy, he said, "is a vulnerability that can be very easily exploited, so of course it will be exploited."

The kids in the study were mostly white and well-off, the researcher said - a group that you'd expect would be targeted less often. So bullying may be more common in poorer and minority children who also have food allergies.

But allergies aren't the only cause of teasing and harassment by peers.

In another study, researchers from Yale University in New Haven, Connecticut, found that almost two-thirds of 361 teens enrolled in weight-loss camps had been bullied due to their size.

That likelihood increased with weight, so that the heaviest kids had almost a 100 percent chance of being bullied, Rebecca Puhl and her colleagues found. Verbal teasing was the most common form of bullying, but more than half of bullied kids reported getting taunted online or through texts and emails as well.

'START THE CONVERSATION'

Shemesh's team found only about half of parents knew when their food-allergic child was being bullied, and kids tended to be better off when their families were aware of the problem.

He said parents should feel comfortable asking kids if they're being bothered at school or elsewhere - and that even if it only happens once, bullying shouldn't be ignored.

"We want parents to know," he said. "Start the conversation."

"Parents whose kids have a food allergy should really be aware that their kids have the kind of characteristic that often leads to being bullied," Schuster told Reuters Health. "They should be working with the school to handle the food allergy in a way that isn't going to make it more likely that their kids will be bullied - and they need to be attuned to their kids."

That's the same for parents of overweight and obese children, he added.

"Kids need their parents to be their allies in these situations," he said. "Their parents can help them still feel strong."

SOURCE: bit.ly/cxXOG Pediatrics, online December 24, 2012.

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