In recent years, sales of air fresheners—especially plug-in air fresheners—have soared. But while sales are up, so are complaints from people who are exposed to the scents at home, at work, in public places, and in the homes of family and friends.

Not-So-Pleasant Scents

Curiosity about anecdotal reports of negative responses to synthetic scents prompted University of Washington professor Anne Steinemann to conduct two epidemiological studies about air fresheners. Each time, she asked more than 1,000 people if they suffered from any adverse health effects, such as respiratory problems and headaches, after breathing in air fresheners.

The results were striking: In the first study, more than 17 percent of the general population and 29 percent of asthmatics said they experienced health problems following exposure to an air freshener. In the second study, reports of problems were 20 percent and 37 percent respectively.

The higher percentages for asthmatics aren’t surprising. “Air fresheners can cause problems for people with asthma or lung diseases like emphysema and chronic bronchitis,” says Dr. Norman Edelman, chief medical officer for the American Lung Association. “Some people with these diseases are exquisitely sensitive to anything in the air that’s not natural and will develop allergic-type reactions.”

As a result, the organization advises against the use of these products if anyone in the home suffers from respiratory problems.

The number of people who are potentially sensitive to these chemicals is significant. Edelman estimates that 20 million Americans are asthmatic, and another 20 million suffer from chronic obstructive pulmonary diseases like emphysema and bronchitis.

In addition, Edelman cautions that even those with garden-variety allergies may want to avoid air fresheners as well: “People with allergies are already suffering from an inflammation of the mucosa. Why add to that inflammation?”

Uncertainty in the Air?

Steinemann’s research, which relies solely on people’s perception of a problem, not on scientifically controlled studies, is not conclusive proof that air fresheners are problematic. However, Steinemann stresses that it would be unethical to conduct direct experiments on people. “You can’t put someone with asthma into a chamber and expose them to chemicals that may trigger an asthma attack,” she says.

While experiments haven’t been conducted directly on humans, research on mice seems to support Steinemann’s findings. A study published in Toxicological Sciences in 2007 found that volatile organic compounds, which are a common component of air fresheners, caused respiratory problems in laboratory mice. In addition, a 1997 study published in the Archives of Environmental Health found that mice experienced significant respiratory distress and irritation, as well as neurological problems, when exposed to a commercially-marketed solid air freshener.

Although more research is needed to conclusively prove that air fresheners are problematic, it’s still worthwhile to take action now, especially if anyone in your household suffers from chronic respiratory diseases (like asthma, bronchitis, or emphysema) or complains of problems after breathing chemically-scented air. After all, using air fresheners is not a necessary part of keeping house: Why take the chance that they will bother you, other members of your household or potential guests?

“Air fresheners are not an essential product,” says Edelman. “If you keep your house clean, you won’t need to cover up bad odors.”