Some suspect the change has something to do with the evolution in how foods are grown and produced, like the crossbreeding of wheat or the use of antibiotics in cattle. But Lio said tests haven't supported that.
Emory's Galina said the new CDC statistics may reflect a recent "sea change" in the recommendations for when young children should first eat certain foods.
In families with a history of eczema or food allergies, parents were advised to wait for years before introducing their young children to foods tied to severe allergies, like peanuts, milks and eggs. But professional associations changed that advice a few years ago after research suggested that allergies were more likely in those kids when the foods were delayed.
The old advice "was exactly the wrong thing to do," and could have contributed to some of the increased cases, Galina said.
The CDC report also found:
— Food and respiratory allergies are more common in higher-income families than the poor,
— Eczema and skin allergies are most common among the poor.
— More black children have the skin problems, 17 percent, compared to 12 percent of white children and about 10 percent of Hispanic children.
The mother of a 13-year-old girl, who is black, runs an eczema support group in suburban Washington, D.C. Renee Dantzler says roughly half the families in her group are African-American. Eczema is an itchy skin condition, which often occurs on the arms or behind the knees. The cause isn't always clear.
Her daughter, Jasmine, started getting rashes at 6 months and got much worse when she was 4.
"Her whole body would flare. If she ate something, you would kind of hold your breath," Dantzler said. "And she's allergic to every grass and tree God made."
Her daughter took to wearing long sleeves and pants, even in hot weather, so people wouldn't see her skin scarred — and whitened in spots — from scratching. She began to improve about four years ago with steroid creams and other treatments and has gradually become less self-conscious about her skin, Dantzler said.
She's now on a school track team, which means wearing shorts.
"She's the only one on the team with long socks," her mom said.
CDC report: http://www.cdc.gov/nchs/