Except for an occasional asthma flare up, Caitlin Murray is a healthy, happy 5-year-old, who loves doing artwork. But three years ago, she was terribly sick, and no one could figure out why.

“She would have terrible headaches and her face was swollen and she’d throw up sometimes for seven to 10 days,” Jill Murray, her mother said. “They tested her for cystic fibrosis, for leukemia, all kinds of diseases and they couldn’t find anything wrong with her.

Caitlin said it was a terrible feeling.

“I was like really, really sick,” she said. “I was feeling like I was going to die in a few days.”

Her mother had a gut feeling that whatever was making her daughter sick was in their Pennington, N.J., home.

“We started working with the head of the diagnostic center at Children’s Hospital Philadelphia,” Jill Murray said. “He said ‘Try it. Leave your house. That’s the only way you’ll know.’ ”

A Scary Find

In the basement, Murray checked inside a crawlspace. There was mold everywhere.

“And with that we just got out,” Murray said. “We literally took the shirts on our backs and left.”

Caitlin’s suffering went on for three years before the girl finally felt better. The Murrays’ experience is not unique. Because modern homes are more tightly sealed for energy efficiency, water — which mold needs to survive — gets trapped inside.

Modern building materials like wood, drywall, wallpaper and fabric are appealing food sources for mold, while building technologies such as synthetic stucco can leak and trap moisture inside. Home appliances including clothes dryers and dishwashers also generate water vapor, again creating the type of environment that mold can thrive on.

Concerns About Toxic Mold

“Mold spores are everywhere,” said Meg Hamilton, CEO of Hamilton Thorne Biosciences. “They’re in your house, in your attic, on the street, in your living room, in your kitchen. It’s a question really of how much and what species.” Some molds are worse than others, said Tom Kelly, a director of the indoor environments division at the federal Environmental Protection Agency.

“There are a relatively small number of mold species that have been identified as producing a kind of toxin called mycotoxin,” Kelly said. “What’s not clear is whether they are toxic to human beings.”

Some industry experts say there’s growing evidence that they may be.

“We certainly are beginning to see strong indications that the so-called toxic mold can make you very ill,” Hamilton said.

Whether some molds are more dangerous than others is just one of the questions researchers like Dr. David Zhang, a research biologist at New York’s Mt. Sinai Medical Center, are trying to answer. There are more than 100,000 mold species, and about 50 are considered toxic. He has invented a DNA-based technology that spotlights the bad ones.

Scientists and doctors do agree on one thing: about one in three people can have allergic reactions to mold. For asthma sufferers who are very young, like Caitlin, or elderly, mold can trigger much more serious problems.

This one family’s life was destroyed by the mold in the house.