Spring has passed, but allergy season in the South gives little relief.

And those who suffer from allergies have welcomed some company over the years.

According to the National Institutes of Health, about 54 percent of Americans are sensitive to at least one allergen, about two to five times higher than 30 years ago.

“We know that over the past number of years diseases that we call atopic diseases are increasing in frequency — asthma, allergies, atopic dermatitis and food allergies,” said Dr. Andy Nish of the Allergy & Asthma Care Center in Gainesville. “We see that in our practice.”

But some health officials are searching for a reason why. Nish said one of the most popular theories is the “hygiene hypothesis.”

At theory’s core is that today’s children are too clean and are not exposed to enough “endotoxins” to help build immunity at a critical age.

White blood cells, called T-helper cells, are produced by the body to help fight infection. But, the theory states, if those cells are not exposed to endotoxins, they have the opposite affect.

“The way this theory goes is that when people are exposed to either infections at an early age or these substances called endotoxins, which are found in the outer part of certain bacteria, then when those T-helper cells come down the assembly line they go in the direction of fighting infection,” said Nish.

“The thought is when there are not those things like endotoxins to shift them into production to fight infection, then they shift the other way and become T-helper 2 cells, which then increase allergies.”

In short, exposure to allergens at an early age may help ward off allergy symptoms.

And many researchers are heading to the farm to test that theory.

Angel Rushing, a local grower just outside of Cleveland, said her two children, Eli, 8, and Tanoa, 10, are allergy free, along with the rest of her family.

“I don’t know about the studies, but I know my kids don’t have allergies,” said Rushing. “Maybe there is a connection and I just didn’t know about it. We just eat the fresh food and the honey and they’re out here all the time.”

Rushing grows a number of fruits and vegetables, as well as keeping honeybees and chickens.

Her children are constantly outside picking or tending to the chickens.

“You would think every time something is blooming, you’d know you have allergies,” said Rushing. “That doesn’t happen with us, so it’s not allergies.”

Actually, she said, her family, outside of a random cold, hardly gets sick. And they are definitely not kept in a bubble.

“Obviously no one would speak against cleanliness — that’s going to be a good thing no matter how you slice it,” Nish said. “But it does look as if, at least partly, our society has become more industrialized, more clean, if you will, more suburban as opposed to rural and the rise of allergies has paralleled that to some extent. And (the hygiene hypothesis) is one theory for that.”

According to the Center for Disease Control, about 7.1 million children last year were reported to have hay fever. More than 8.5 million were reported to have respiratory allergies, 3.4 million with food allergies and 9.4 million with skin allergies.

But, Nish said, the theory is not proven.

“It’s not fully explained or proven, but it’s a potentially attractive theory,” he said.

It may not be just as easy as taking children to the farm, either.

“I don’t that we can translate that into: ‘Be sure you take your kids to a farm before they’re X number of years old,’” said Nish. “There’s also potential infectious exposures that may outweigh the benefit of being in that situation.”

But for now, Nish said, treatment for allergies is readily available.

“Fortunately, we have very good treatments for asthma and allergies,” he said. “So it’s not something that can’t be dealt with. But certainly if we can decrease instances of it that’d be great.”