Last year, Tamara Schuster showed a family a house in the Chicago suburbs that had a history of mold. Schuster, a Naperville broker, said that the building was “mediated” for mold and “essentially fixed,” but still she encouraged the potential buyers to look elsewhere.

Today, doctors and experts in real estate are encouraging homeowners more and more to be wary of a sick home.

“If I saw something that wasn’t right, I wouldn’t even consider buying it,” Schuster said.

When it comes to the thought of an unhealthy home, “More people are worried than they used to be,” said Jim Sublett, indoor environment chair at the American College of Allergy, Asthma and Immunology.

Mold is not the only contributor to sick building syndrome. According to the EPA, other factors include inadequate ventilation, chemical contaminants from indoor and outdoor sources (i.e. carbon monoxide, formaldehyde, vehicle exhaust) and various kinds of bacteria.

Whatever the problem — it can be building-wide, or specific to a room — it can have a drastic effect on one’s allergies and immune system and it can also lead to asthma.

“Most people don’t think of their home as an entire building,” Sublett said. “Let’s say you store pesticides, or leave your car running a bit long in the attached garage.” These are two prominent examples of people bringing in contaminants to their entire home without knowing it, he said.

And for those living in apartments, ”Sometimes you can live on the fourth floor, but what’s happening on the first floor can affect your air quality,” Sublett said. “You may have someone on the first floor that’s a heavy smoker and someone on the fourth floor who has a strong allergy,” he said. The smoke can affect the health of the person on the fourth floor and of people throughout the building if the apartment complex doesn’t have individual venting for each unit, he said.

There are standards in the real estate world that recognize building-related health concerns. For example, home sellers must fill out a disclosure form saying that a house has a history of mold, Schuster said. “In reality, all homes have some level of mold. But if there’s an elevated level, you have to get rid of it” before selling, she said.

Connie Atterbury, a real estate agent in downtown Chicago, has less experience with the problem. “A lot of the problems have come in the suburbs where new construction is,” Atterbury said.

A couple of possible structural contributors to sick homes seen in new-construction suburbs are some Chinese drywall and homes constructed with “split-block” bricks, Atterbury said. The bricks “need to be sealed or else they leak, and that creates mold,” she said.

The problem with what people may think is a sick building is that it is not absolutely identifiable, said Alvin Fox, professor of pathology, microbiology and immunology at the University of South Carolina. The main proven contributor to sick building syndrome is bacteria from shed skin in heavily occupied buildings, according to data he and his researchers gathered.

Just because someone can see and smell mold, and just because they claim they feel sick, is not strong enough evidence to say that’s what is causing them to be sick, he said.

Schuster was adamant that she and her colleagues don’t recommend potentially sick homes to clients. “If I ever had a doubt about anything, I would err on the side of caution,” she said.

In her neighborhood, she said, building concerns are not prominent. "Basically, because the land value is higher, people tend to take better care,” she said. “There are generally higher standards all around.”

Sellers, Schuster said, “Always have to disclose if there are issues” with a building. If they don’t, they can become liable, but “only if they knew” something was wrong, she said.

“I encourage buyers to get a thorough home inspection,” Schuster said. “That can eliminate most problems.”